# Rainbow Fish & Mollies



## Storiwyr (Apr 24, 2012)

So my husband and I are in the process of setting up a 20 gallon tank for Mollies. I have been trying to research them online, as far as optimal water parameters, potential tankmates in that size of tank, etc. What I'm discovering is how spoiled I am by this forum. I just am having no luck finding consistent information I trust on Mollies. I think I've pieced together enough information now that I think I can do 1M:3F in the 20g just fine with regular water changes. I'm doing sand substrate, some rocks, and some live plants. I would like to use the same Rift Lake mix on my 20g that I do on my 75g Lake Tanganyika tank, so I can safely keep a filter cycled on the 20g for a hospital tank that I could use for either the Lake Tangs or the Mollies. That would put the pH for the molly tank at ~8.2 with higher hardness (I can get exact numbers for that, just don't have them on hand right now). I have read that mollies should be fine at that pH and hardness, and that they may even prefer it. Does higher hardness mean brackish water, or is the water still freshwater, just with higher pH and hardness? I'm not sure whether the term 'brackish' refers to salt content only, or if raising the hardness involves using salt?

I had read about Rainbow Fish species being good possible tankmates for mollies. Does anyone know if this is true? Can Rainbow Fish be successfully kept at Lake Tang pH and hardness?


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## DJRansome (Oct 29, 2005)

I always thought ideally mollies were kept in brackish water, which has salt content...NaCl. Not what is ideal for Tangs.

And I believe rainbows are good with a higher pH but they are not brackish.

Some of my reading about rainbows suggested their ideal is a fairly large tank planted with tall plants like vallisneria.

Won't a population of mollies pretty much suffice for stocking a 20G?


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## Storiwyr (Apr 24, 2012)

I really wish there was a mollies-forum site!

I'm seeing so much conflicting information on proper care of Mollies.

So here's a new question:

1) If I do brackish water and a pH of 7-8 in the Molly tank, can I still keep a filter for the hospital tank cycled on it? Or will the beneficial bacteria be adapted to brackish water and lower pH, and be killed if they are moved to a higher pH, non-brackish environment?

I guess I can get a different type of HOB for the hospital tank and just pull media from my Tang filters ... Hmm. Think think think.

Maybe I'll just do a few more female Mollies and a bottom feeder of some kind that won't eat Molly fry. I read in one place that Mollies are an estuarine fish. If this is true, then brackish water would be their natural habitat. But it would also explain their ability to adapt to freshwater or saltwater conditions, even if those aren't strictly optimal. Some other sites I read said that brackish water was better only because Mollies are prone to disease ... if that's the case then I would think that prone to disease may be the result of the fact that Mollies are often sold as 'starter' or 'throwaway' fish, and probably often kept by people who are not as rigorous in their tank maintenance as they should be. I've already learned careful tank maintenance from keeping cichlids.

I'll do some more research into Mollies in the wild and try to match their natural habitat.


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## Fogelhund (Dec 3, 2002)

Mollies are naturally a brackish water fish. They are prone to ich, which really doesn't have much to do with beginners.


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## Chromedome52 (Jul 25, 2009)

Actually, there is a forum for information about mollies and other livebearers, the American Livebearer Association site (www.livebearers.org).

Mollies will do fine in very hard water without salt, and I've also seen them used to cycle Marine tanks; just don't take them from one and put them directly into the other. Moving them from heavily salted water at the fish store and putting them in fresh water weakens them greatly, and they then become susceptible to ich and other infections. Most of the ones I collected in Florida were in brackish areas, but there are places where they are known to occur naturally in fresh and marine. I'm assuming you are talking about Sailfin Mollies, of course. The common Black Mollies are NOT brackish, they come from hard water areas in Central America. There are also some populations in brackish areas, but those are considered by some to possibly be different species. There are a number of species, and most domestic Mollies are hybrids of several.

_Melanotaenia_ Rainbows will do well in hard water. They can get along with mollies, but a 20 really isn't big enough for most of the larger Rainbows. However, I do not have a lot of experience with them, as they do insist on clean, unpolluted water and often a good current.


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## Storiwyr (Apr 24, 2012)

Thanks guys.  I think I'll just stick with mollies and some sort of small cleanup crew. A BNP or something. The one molly I currently have is in 8.2 pH with no salt, can I put him in mildly brackish water without shocking him? He's black, but I'm PRETTY sure he's a Sailfin, not a shortfin.

What about using the tank to cycle a small filter for use on a hospital tank? Will it screw up the bacterial colony if it goes from lower pH to higher pH or brackish to nonbrackish? Or do the Nitrifiers not care?


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