# 2 Canisters Needed For 3D Background?



## JP_92 (Aug 2, 2013)

I'm putting a 3d background in my 75 gallon tank and I plan on hiding everything behind it. I'm worried that having the filter behind wont be sufficient for keeping things clean. I currently have an Aquatop cf-500 canister rated for tanks up to 175g. Would that be enough or should I get another canister and have them on each side?

I know I need to put some holes in the background as well although is it better to put a few larger holes or many small holes in? I know a lot of you guys have 3d backgrounds so what's the best method to keep my sand from having too much waste build up?


----------



## DJRansome (Oct 29, 2005)

What is the GPH of your filter?

I like having 2 canisters and have 4 holes in one background and 2 holes in the other. Both work fine.

In my 36" tank I have 2 holes and one filter intake positioned in between them. You need to keep both the substrate clean but also the space behind the background.

With the 3D ones I like to choose the hole location in a thin part of the background and also under an overhang so they are less obvious. This can also dictate the number of holes.


----------



## JP_92 (Aug 2, 2013)

It's rated at 525 gph. When my 75g was still active without a background I had an extra submersible filter that put out around 250gph as well which helped keep the sand fairly clean. I'm leaning towards another filter or powerhead/pump thing to keep the waste suspended long enough to make it through the background holes. The filter obviously would be a better option as it would add a stronger suction through the background while providing water movement through the output but **** my costs keep rising! haha

Initially I saw someone say to drill a lot of small holes in hard to see places but your low number of holes sounds better to me. I think it will create stronger suction of water from front to back since a higher number means the background is more permeable. I'd imagine you'd want to aim for a hole or 2 holes that in total are equivalent to the diameter of the intake to maximize suction. Oh and of course like you mentioned place the intake near/in between.

DJ how's your suction on your set up at your hole locations? Would you say it's fairly strong? It must be weaker than near the actual intake in the back I'd imagine. Also anyone else with info or thoughts, feel free to chime in.


----------



## JP_92 (Aug 2, 2013)

By the way, I've read all the threads I could find on 3d background. Thought I'd add this in here since it's relevant, you wont have to repeat yourself and it could help potential readers that stumble across this thread one day. haha DJ you might be the expert from what I've seen!

Re: hiding equip,& water movement behind 3d b/g Post by DJRansome » Sat Oct 06, 2012 8:18 am 


DJRansome said:


> On a 48" tank I usually do two filters and two inlet holes. Behind the BG things are arranged like this:
> Filter Inlet pipe > Heater > BG inlet hole > space > BG inlet hole > Heater > Filter Inlet Pipe
> 
> With the suction at each end, the entire space behind the BG remains clean. Equipment is grouped at each end.
> ...


----------



## DJRansome (Oct 29, 2005)

Update: I use in line heaters for the big tanks. And I use a 2 or 2-1/4 inch hole saw that attaches to a drill for the holes. I think my first background install instructions suggested 2" holes.


----------



## JP_92 (Aug 2, 2013)

I had no clue about inline heaters. That would be a great idea and something I'll look into!

I think I'm going to just get another filter. I was never pleased with using just one on the 75g before the background so I don't want to risk it.

As for holes I haven't committed yet but I'm thinking I will drill 2 holes the diameter of each intake only. Pretty much I want to maximize the suction from front to back. I'm looking for the sweet spot right before the holes are too small to not allow enough water behind to keep the level at full. I really only want to drill once so if anybody thinks this is wrong please let me know. All criticism welcome!


----------



## Deeda (Oct 12, 2012)

I would think you want the holes larger than the intake diameter to allow for the possibility of the holes getting plugged by plants, decor or a dead fish.


----------



## Prognathodon (Mar 31, 2016)

From a hydraulic point of view, the incoming flow of water will have a conic shape, so you want the hole in the backdrop to be bigger than the actual intake so that the hole in the backdrop is not acting as a restriction. If I was at work with my big "Standard Handbook for Civil Engineers" I could probably even find a formula for it, but I'd probably go with a slightly bigger hole by eyeball/gut.

The first picture here demonstrates the contraction:
https://en.m.wikipedia.org/wiki/Vena_contracta


----------



## JP_92 (Aug 2, 2013)

Good point Deeda! I didn't take that into consideration.

Thanks Prognathodon! Your post was exactly the type I was looking for. I studied mechanical engineering in college and was thinking about digging out an old fluid power textbook if I still have it but I understand what you mean. The bigger hole will prevent restriction yet still give the same amount of suction just with the highest concentration point actually occurring behind the background. Ideally to hit maximum suction you'd want that highest concentration point to be equivalent to the diameter of the intake, not the hole itself. Still would need to take into account Deeda's point as well though and any filter cap added on the hole too. I can probably track down the equation myself if I feel the need to. It would be nice to know the minimum hole size as a safety precaution but I can probably just wing it.


----------

