# Suitable Tank Size - discussion



## DeadFishFloating (Oct 9, 2007)

First off, please no one take this discussion personally. I am not taking a shot at any particular individual/s. I bring this up becuase I often see, and am involved in many such discussions here, and often fail to understand other peoples reasoning. However such discussions often take a thread off the OP's original question.

I often see in discussions people suggesting that certain species can or can't be kept in _x_ size tank. That's fine, we all have our on beliefs on what size fish can be kept in _x_ size tank, we (I) just have to accept that not everyone views the world the same.

However what I often struggle to understand why people suggest to upgrade to a 75/90 gallon tank from a 55 gallon tank. If a fish is outgrowing a 4 foot 55 gallon tank, surely the next logical step is a 100 gallon 5 foot tank, or a 125 gallon 6 foot tank.

I do understand that a 4 foot tank could be adequate in length, however a 55 gallon might not offer the foot print necessary to adequately aquascape for multiple territories. So the next logical size tank is a 75 gallon, with an extra 5 inches in width. However if a 75 gallon tank isn't really suitable, then surely a 90 gallon won't be. It just offers a couple of extra inches in height and more water volume. So logically a 120 gallon is the answer instead of 75/90 gallon tank.

Obviously not everyone has the financial means, or the space to upgrade a 4 foot tank to a 6 foot tank, but this brings up many other associated discussions on researching suitable cichlids for your situation, etc.

So anyone want to comment or will another of my threads fade into the nether regions of the forum.


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## Joels fish (Nov 17, 2007)

I think your your dead on here with this in principal anyway. There are no hard answers to this issue , but you've certainly come closer than most on the subject .


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## dwarfpike (Jan 22, 2008)

When I recommend a 75 or 90 over a 55, it has to do with the length of the fish. Take a JD for instance ... I wouldn't keep an 8+ inch fish in a tank with only a 12" width. Hence I recommend a 75 for JD's ... that extra 6 inch width matters. I personally don't like to keep anything longer than 6" inches in a 12" width tank. This only works with milder fish (jd's and sevs for example).

But there are other reasons such as territories that require a larger tank both width and lengthwise. Red terrors are a good example. A pair can be kept comfortably divided in say a 125/150 range tank, but if you want them undivided you would need more of a 180/240 range. With such a fish, a simple expanding of the width just isn't enough like the 55 -> 75.

So it comes down to the fish in questions needs for floorspace, but most of the questions asked are about milder cichlids (oscars, jd's, sevs, gt) hence why the 75 gal seems to be most people's answer.


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## DeadFishFloating (Oct 9, 2007)

> I wouldn't keep an 8+ inch fish in a tank with only a 12" width. Hence I recommend a 75 for JD's ... that extra 6 inch width matters. I personally don't like to keep anything longer than 6" inches in a 12" width tank. This only works with milder fish (jd's and sevs for example).


See this is where different people have different ideas on what is acceptable for fish. I wouldn't keep an 8 inch fish in a 4 foot tank. However, a LFS near me has a 120 gallon display tank with a pair of large Gold Severums as the show piece, and they look fine in it. However I've seen a similarly sized Green Severum in 75 gallon tank, and just looked wrong.

I guess it may also depend on how active a species is. Something like a GT or JD needs the room to move, yet most Severums would struggle to get out of second gear.


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## naegling23 (Jan 4, 2008)

I depends on a lot of factors.

For one, longer fish may need space to adequatly turn around, so a 75 might be better than a 55. For smaller fish, like dwarfs, the 75 can give you enough space to have front and back territorys which a 55 does not allow. It also allows you to add more depth to an aquascape.

for the 90, there is more volume of water, so for larger waste producing fish, the extra volume could make a big difference, think pair of oscars.

I think the issue is that once you get to the 55 gal. territory, and even more so beyond, the cost starts to become a major issue. Larger filters, more lighting, stands, the tank itself. Add onto that the extra floor space a larger tank takes up, and floor stability (a 120 gal might not be the best choice for a second floor bedroom in an older house). So, the 75/90 are recommended because they may be a better size than a 55, but can still fit into the house and budget of the tank owner.


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## Number6 (Mar 13, 2003)

A standard 90g tank is no better than a standard 75g tank because (as you point out) the only difference is a bit of height.

However, there is a big difference in what can go in a 4 by 12, vs a 4 by 18 and finally a 4' by 2'... 
In my experience, it is all about the fishes perceived space more than actual space... line of sight breaks are a prime example.

heck, with this in mind, I've added fish that should be in 4ft tanks to a 2 ft tank with a 22" by 18" tall bit of slate - splitting the tank into "2"... by the time the dominant fish chases the subordinate around that rock three times, he gives up...

in a 12 inch wide tank... well, that subordinate fish just never really "leaves" the dominant fishes perceived territory. It just hits the glass wall, gets bit, then foolishly goes BACK into his territory! :lol:


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## Dutch Dude (Sep 14, 2006)

> A standard 90g tank is no better than a standard 75g tank because (as you point out) the only difference is a bit of height.


I don't agrea on that. Fish like wild angels and Discus will apreciate the extra height. When the floorspace is limited and a 4 ft tank is the maximum size you can put there I do suggest the 90 gallon. It does have a larger volume and especially with community tanks it is nice to give the fish some more space or add 20 tetras in stead of the standard 8.

Large fish need large tanks thats for sure. Depending on the fish specie the floorspace may be more important as the volume of the tank. A large footprint and large length allow larger or more territories.

I suggest to buy the largest tank you can place or afford or,.....buy multiple tanks like Peter did :wink:

I wish people would be more interested to the natural territory size of a fish specie and also count that to be one of the main factors of buying a fish or tank and aqua scape it.


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## dwarfpike (Jan 22, 2008)

I think angels and discus are the exception, although a common exception of course. I prefer 75's over 90's usually for most cichlids, of course if keeping angels or discus though I'd get the 90 of course. They are deffinately two fish that have a vertical requirement. But usually, 75's cost much less than 90's around here, and look more proportional and easier to aquascape.

*DFF* - I think I've read before you all don't have standard tank sizes down there ... here a 4' 120 gal means it had a 24" width to as well as height ... which equals one happy sev. :lol: With a tall and long fish like a sev, that extra 6 inches from a 75 to the 120 as well as the extra hieght would matter, hence why it looks fine in one and not the other.


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## DeadFishFloating (Oct 9, 2007)

*dwarfpike* we do have standard tanks down here. But being so close to asia (read China) many LFS are starting to import acrylic tanks, such as my large one, at a much cheaper cost. Basically you get the tank, cabinet, hood with lights and trickle filter built into it. Even locally based tank makers are now importing the glass they use from China.

I've had to really hunt around to get the best buys for my two new tanks. If it wasn't for our local (State) aquarium forum, I would of just bought two more acrylic tanks. But I like the idea of glass tanks.

So, yes I know a standard 120 gal is 4'x24"x24". It's they next tank on my list to buy.


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## dwarfpike (Jan 22, 2008)

I have always prefered glass to acrylic tanks myself ... two reasons, those rounded edges drive me nuts and I like the larger openings on glass tanks versus those tiny ones on the standard arcylics. Though I have now seen them without the rounded sides, so if it's a fish that I need a wet/dry for (_Satanoperca daemon_ comes to mind) I'll eventually go acrylic.

As for sizes, since I keep cichlids I probably won't own a 55 gallon unless I pick it up for free. I rather save an extra month, and pay the little bit more for the wider 75 gallon just for territory issues with the fish we keep. Or save for several more months and get a 120 ... though honestly, given the smaller cichlids I keep, I'd probably go for the 5-6 foot versions over the 4 foot ones ... unless I made the jump to full sized pikes of course like lents or marms.


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## Number6 (Mar 13, 2003)

I can't say I've noticed a single speck of difference in Discus or Angelfishes behavior when put into an 18" deep, 21" deep vs 24" deep tanks. What differences in behavior are folks seeing?

As for the extra water volume between a 75g vs a 90g tank... a sump adds far more water volume so IMHO a 75g with 30+ sump is still the way I go over 90s. Removal of filter pipes, heaters, and other junk to the sump is an added bonus and allows for even more flexibility in aqua-scaping.


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## dwarfpike (Jan 22, 2008)

I haven't noticed behavior differance, but I have noticed growth differance.

This may be hold true as it was simply one time, but my angels in a 40 breeder (16" tall) did not grow as long of dorsal or anal fins compared to my friends that had them in a 24" tall 120. I did more water changes and fed more than he did, we got the angels from the same place so I think they were siblings. But was it the extra gallonage or the height that made the differance? Given the larger number and percentage of water changes I did, I am guessing the height but there was really no way to prove this.

So for normal (scalare) angels I want at least a 20" inch hieght now a days. I could be paranoid though.


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## Number6 (Mar 13, 2003)

I'd blame stress from the confinement/physical interactions between fry in the 40g breeder... I've experienced the same thing with multiple fry in different tanks as well as noticing that very small numbers of fry seem unaffected by tank size...

The 40g to 120 is likely explained that way as opposed to height...


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## Dutch Dude (Sep 14, 2006)

> But usually, 75's cost much less than 90's around here, and look more proportional and easier to aquascape.


 Thats so true but sometimes the 15 extra gallons give some more relive to stock levels or like I mentioned will be appreciated by fish like Discus and Angels. Deep tanks (wide) will suggest a larger depth when properly aquascaped but that doesn't mean that 90 gallons are so difficult to aqua scape. You can check out the old set up of my 90 gallon planted geophagus tank in my profile. The large plants along the sides and the driftwood against the background created lots of dept.

A sump does add more water body but not everyone is fund of a sump. A sump can be risky if it comes to overflows and pumps and also contribute to humidity. So if you are not aiming at a sump as filtration system the 90 gallon can add just the 15 gallon extra.

Over here we have diferent tank dimensions. Some examples.

52 gallon = 16 wide x 20 high x 40 long
65 gallon = 16 wide x 20 high x 48 long
79 gallon = 18 wide x 20 high x 48 long
94 gallon = 18 wide x 24 high x 48 long
105 = 18 wide x 20 high x 64 long
131 = 18 wide x 20 high x 80 long
and of course custom tanks of 24 high in stead of 18 high. I left out the smaller tanks. Sizes are US gallons.

Acrylic tanks are rare over here and over priced. We can get better qualety with all glass tanks.

As for Discus in high tanks,...a 20 high is doable but 24 gives them just the extra space they need. It also depends on tankmates and aquascape. By the way, if you talk abouth a 18 deep tank, are you talking abouth the wide or the height? As for growth issues and tank height,....I realy would not know,.....back to DBS his discussion,....I'm not experienced with that :wink:


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## Number6 (Mar 13, 2003)

Dutch Dude said:


> As for Discus in high tanks,...a 20 high is doable but 24 gives them just the extra space they need. It also depends on tankmates and aquascape. By the way, if you talk abouth a 18 deep tank, are you talking abouth the wide or the height? As for growth issues and tank height,....I realy would not know,.....back to DBS his discussion,....I'm not experienced with that :wink:


When I mentioned deep, I do mean height of tank. You mention that you notice something from a 20" high and a 24" high? What effect do you see in the Discus?


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## DirtyBlackSocks (Jan 24, 2008)

Altum angels and high bodied discus need 24" tanks, aside from that it's a misconception that either fish need anything over 20" - I think most of it stems from people seeing them use the extra space because they're placing them in say a 90 gallon from a 100 gallon - where the difference in length to height is there - if that makes any sense.

Either way, 24" is still ideal for discus and angelfish, but 20" should be considered the bare minimum for adult specimins....and like I said, altums are a whole different ball game.


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## Dutch Dude (Sep 14, 2006)

During quarreling the weaker fish does have more room to escape and uses the height of the tank to avoid a confrontation.


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## Toby_H (Apr 15, 2005)

If someone has an Oscar in a 55 Galâ€¦ I would consider moving it to a 75 gal a logical upgrade. Although it is still a 4â€™ tank the extra 6â€™ front to back will still hold benefit. I am not saying this would be the best upgrade, but it would be a logical upgrade.

If someone has say a Dempsey and a GT in a 55 gal and they arenâ€™t getting along (both males). Then a 75 gal probably wonâ€™t buy them much extra time. In this case each fish desires itâ€™s own territory and the trick here is to move the territories further apart, not making them more roomy (front to back). In this situation I would suggest a longer tank. I would even venture to say a 6â€™ x 1â€™ tank would suit them better than a 4â€™ x 1.5â€™, although neither would really suit the two fish.

Each situation has itâ€™s own details and â€˜the bestâ€™ option will vary in every set up. This is why there is no replacement for experience. The more we watch our fish grow, develop and change the more we understand about their needs. It seems like every year I â€˜trulyâ€™ understand something that I thought I truly understood last yearâ€¦ and I assume next year Iâ€™ll understand it even betterâ€¦

Iâ€™ll always argue that a 90 has advantages over a 75... I canâ€™t say itâ€™s â€œbetterâ€


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## PsYcHoTiC_MaDmAn (Dec 26, 2005)

I try and give a minimum amount of room to the fish, taking the adult length and multiplying by 6 for the length and by 2 for the width. this would be the MINIMUM size tank I'd be happy to keep a fish in.

the vast majority of my tanks offer much more swimming room for the fish (almost all (permanent tanks, not grow outs) offer 12 times their length to swim in)

I've seen a lot of big fish (oscars, severums, big CA's) kept in 4foot tanks, and I just dont think thats fair, its the equivilent of living your life inside a telephone box..

the minimum I'd keep something like an oscar in is a 180. I'm considering (after I built my fish shed) building a tropical pond (6by4by2-3 maybe wider) and keeping some rays and large(ish) cichlids, but I would never be comfortable keeping large active fish (such as arrowana, large predatory cats or BIG cichlids such as peacock bass & dovii) without something the size of a small swimming pool


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## DeadFishFloating (Oct 9, 2007)

G'day guys,

Thanks for contributing to the discussion.

I didn't intend this discussion to move towards what sized tank is suitable for certain species of cichlids. We have had that discussion many times and *PsYcHoTiC_MaDmAn* we'll just have to live with the fact a lot of other hobbiests don't see things the same way we do. Or is it they'll have to learn to live with us. :lol:

:roll:

However, early on in the discussion a couple of posts mentioned that they would recommend an upgrade to a 75 gallon tank from a 55 gallon tank, if the 55 gallon tank didn't offer enough turning room.

For me this is where I lose track of some peoples reasoning. (And yes I do know it does fall back on to what people view as a suitable sized tank for _x_ sized fish) Surely if a 55 gallon tank isn't wide enough for a fish, then a 4 foot tank really isn't long enough for it. So the natural progression should be a 5 or 6 foot tank that's atleast 18 inches wide.

And yes I do know it does depend on more than just a fishes size. Like I said before, I don't think a 4 foot tank is a suitable sized tank for a Severum, yet I see a large pair in a 4' by 2' atleast once a fortnight and they look happy and healthy.


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## Toby_H (Apr 15, 2005)

For a hobbyist to make a guideline for themselves such as PsYcHoTiC MaCmAn has, is extremely respectableâ€¦

I try and give a minimum amount of room to the fish, taking the adult length and multiplying by 6 for the length and by 2 for the width. this would be the MINIMUM size tank I'd be happy to keep a fish in.

Yet to advise people new to fish keeping that this is the minimum size tank a fish can be housed in is (in my opinion) a complete exaggerationâ€¦ that isnâ€™t the minimum that they can live their live in without experiencing harm due to tight quarters, which is what I think people mean when they say â€œminimum requirementsâ€


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## Dutch Dude (Sep 14, 2006)

> I try and give a minimum amount of room to the fish, taking the adult length and multiplying by 6 for the length and by 2 for the width. this would be the MINIMUM size tank I'd be happy to keep a fish in.


What a nice guidline! :thumb:

The only thing people hardly talk abouth is the size of their natural territories. Some specie have small territories and some (mostly more temperament) do have large territories. What are the opinions abouth that???


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## Number6 (Mar 13, 2003)

DeadFishFloating said:


> Surely if a 55 gallon tank isn't wide enough for a fish, then a 4 foot tank really isn't long enough for it.


 That does not seem a logical assumption... if 12 inches is too short, then 4ft is also too short?

I've seen acrylic 4' by 4' tanks... there's almost no cichlid that can't be kept in that tank. Would you suggest that a 4' by 4' is a illogical upgrade to a 55g tank for a 12 inch fish?

What about a 4' by 2'? Does this not provide significantly more 3d space for the fish to swim, turn, etc?


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## jcushing (Apr 6, 2008)

upgrading a 55 to a 75 is the first symptoms to materialize of MTS. it still wont be big enough so youll just be putting off the eventual 6fter, so then youll have the 29g you started with (and probably had little success with) , the "big" 55 you upgraded to to solve your overstocking problems, the bandaid fix of a 75 then the inevitable 6fter. of course once you upgrade your tanks you have to find something to do with the old tanks too


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## GBSTEVE (Dec 10, 2007)

I have to admit, I find referring to tank size in gallons rather strange (we Brits are strange, maybe? :lol: ) I always think in terms of length, depth, height when considering tank size for any fish, how much actual water the tank holds is not really relevant? . As already stated, Physical size of the adult fish , breeding territory (and whether it is to share quarters with another fish needing territory) is much more important than any "length of fish in a given volume formula" as well as the fish's preferred swimming space (upper, mid or substrate dweller) reflects on the height of it's quarters.
PsYcOtIc MaDmAn - Great formula IMO


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## DeadFishFloating (Oct 9, 2007)

G'day *Number6*,

OK so maybe my way of thinking is a little more wierd than for your average wierdo.

But to my way of thinking if a 12inch wide tank doesn't really provide sufficient turning room for a fish, then the 4feet of length really doesn't provide much room for it to have a decent run. It's left to slow cruise it's entire existance.

This is where each individuals personal belief into what constitutes an appropriate size tank for _x_ fish comes into it. *GBSTEVE* expressed it a whole lot better in his post, than what I have managed to. The only reason we talk tank size is that we all know the standard sizes, and it's easier to say a 180 gal as opposed to saying a 6'by2'by2'.

As for the 4'x4' I'd love to see one, but would still prefer to keep a Peacock Bass or Arrawana in a 8'x2'.


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## PsYcHoTiC_MaDmAn (Dec 26, 2005)

DeadFishFloating said:


> As for the 4'x4' I'd love to see one, but would still prefer to keep a Peacock Bass or Arrawana in a 8'x2'.


whereas, I feel a tank that size is woefully small for such a species. imagine keeping a neon tetra in a 6"by1" tank, people would quite rightly tell you its unfair.

given peacock bass and arowana can achieve 3foot, the MINIMUM I could contemplate keeping them in is 18by6 needless to say, well out of almost all hobbyists capabilities. and note, that would be the minimum size. You take the arowana for instance, that thing is designed to cruise all day.

If I were to keep such species, I really would be looking in investing in something like the big pools (metal frame and liner in it, sold as temporary swimming pools) with something like a 16-20foot diameter.

the fact is, my idea of 6length2wide is somewhat basic, there are some species (very active danios and tetras for instance) that will need more room because of their behaviour, whereas others despite their size would require less due to their lack of activity (I'm thinking lungfish here)

however, the issue of stating gallons vs dimensions is something that also annoys me. I may well be purchasing six 55g, however, these have significantly more room than your "standard" 55g. as these would be 48by18by15tall, as opposed to 48by13by20"tall. same amount of water but more footprint, which means theoretically you can have more cichlids in it (at the expense of requiring more water changes to keep it clean)

Dutch Dude, when you get into the territorial behaviour of fish thats a whole different ball game. so much of it comes down to the individual fish. take TFG's big tank, he has quite a few oscars in it and they seem to be getting on pretty well. I've seen shots where it appears that several oscars are schooling, yet I seem to recall they usually stake a territory 12 times their length in diameter (no idea if thats correct, thats the thing that I remember anyway) and the 1 photo where this was particularly visible was in a tank of 8.5feet long (264g) (apart from the topic there are some FANTASTIC photos there)


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## DeadFishFloating (Oct 9, 2007)

Hey *PsYcHoTiC_MaDmAn*,

I wouldn't persoanally keep a Peacock Bass or Arawana in a 8 foot tank either. It was just a sort of [irony]smart[/irony] answer in response to *Number6's* question about a 4'x4'. Which certainly is a bit rude on my behalf, so apologises *Number6*.

But this discussion is starting to gravitate towards what constitutes an appropriate sized tank for _x_ fish. And, as has been established before, everyone will have a different opinion here, and there is the potential for noses to be put out of joint in such a discussion, and this was never my intention.

My ideas on appropriate tank sizes and stocking levels are pretty well known, and all that can be achieved in such a discussion is two sides trying to justify thier _choices_ and many people fading into the back ground if they feel others might look on them unfavourably becuase of thier tanks.

I just wanted to know why many people suggest a 75/90 gallon tank as an upgrade from a 55 gallon tank, and not a 5/6 footer. It appears, and not for the first time, my idea of a standard progression is different to the majority.


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## DeadFishFloating (Oct 9, 2007)

jcushing said:


> upgrading a 55 to a 75 is the first symptoms to materialize of MTS. it still wont be big enough so youll just be putting off the eventual 6fter, so then youll have the 29g you started with (and probably had little success with) , the "big" 55 you upgraded to to solve your overstocking problems, the bandaid fix of a 75 then the inevitable 6fter. of course once you upgrade your tanks you have to find something to do with the old tanks too


Good Post. :lol:

See this illustrates perfectly my way of doing things. I started with a 150g, then went for a 35g and now am working on two 50g's. Who needs to follow conventional thinking or ways of doing things.


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## Toby_H (Apr 15, 2005)

I think that price is the biggest factor in defining the next upgradeâ€¦

Not everyone with an overstocked 55 gal is sure they like the hobby enough to drop $600 on a 6â€™ tank and standâ€¦ but $350 on a 75 gal might be worth investingâ€¦ and is still an â€œupgradeâ€


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