[John]

Thanks guys.

How much would an internal filter cost? What brand and size?

To save money, I would prefer to use one of the two 55-gallon-size filters I already have, one of which is hang-on-the-back power filter and one of which is hang-on-the-back canister. But I won't if you don't think I should. Plus I'd have to get an extension for the intake tube, and I don't know if I'd be able to get a long enough one.

I already have 100 pounds of play sand, but the only reason I got it was because it was so cheap. I knew I might not be able to use it. It's dirty and a little ugly, and I would prefer a lighter-colored sand. Plus most of the people I've talked to say I shouldn't use it. So if I don't use that, what type should I get? It will be exponentially more expensive, right? Where should I get it? What does play sand do to hang-on-the-back filters? Will other types of sand do that? Why doesn't it affect internal filters in the same way?

And lastly, disregarding tank size for the moment, are Mudskippers + Fiddlers/Mudskippers + Archers/Fiddlers + Archers compatible in theory?