I'm thinking black cause I do like the depth aspect. I have blue in my 20 now. It is nice and bright. But I like the idea of the colors standing out with te black as well.
Thanks all for you opinions. Maybe I should jut get more tanks and do each and everyone of the suggestions haha. Don't know how the gf would feel about that tho lol

I keep mine clear, but that's also because there's a window behind so you can see the outdoors through it. :) I'd vote black though, although I'd like to see what mirrored backs look like in practice.

I wouldn't do mirror..... I would think it would be stressful to your fish..... I know when I put a mirror in front of my tank my more aggressive fish go ape..... I say it really doesn't matter what color you choose..... You can usually only see parts of it because your rock will block most of it and unless your super ambitious and keep the back glass clean, it will cover over with coraline and be invisible anyway

What about pond foaming the back wall of the tank. Adds dimension and helps with the nitrogen cycle.

"Don't know how the gf would feel about that tho lol"

Remember it's easier to ask forgiveness than permission

Only thing to consider with this is that you only put the mirror there every so often, so it's a change. If the mirror is there 24/7, they just get used to it. Who knows... it might even take an aggressive fish's anger down a notch...?

My mirrored tank was a cichlid tank and for a while they would swim into the mirror Challinging there reflection. After a week they paid no attention to it. Also note that it was a 90 gal. With 40 cichlids male and female. So I don't think aggression is a worry. But. You do notice any algae Alot more

It doesn't matter. Just let the coraline cover the back glass.

If you must paint it, I vote for black. It does add depth, but equally important - it is the least distracting. Blue is nice and calming, but only because you notice it. Black fades to nothing.

- Brad

At the pet store (Petsmart, I think) they had rolls of background that had black on one side and blue on the other. Initially I went with black but later turned it to blue on my 15G and liked it much better. To me it added more depth and gave it more of a reef look... like you were in the water and looking into the abyss of the ocean beyond.

If you're stuck, see if you can find that kind of background. Then try both sides and think about what you like more. If you ever change your mind, it's a quick fix to change anyway.

I use this blue seascape and it really give depth to the aquarium...very nice! It's a double-sided background.

http://www.thatpetplace.com/images/large/243687.jpg

http://www.thatpetplace.com/pet/group/6645/product.web

http://www.amazon.com/Seascape-Doubl.../dp/B001XYI0TK

This should also be available at your local pet store.