Just saw this. Yes, you can still buy under gravel filters. I'm not using one now on my 90, but sometimes wish I had. While they do make the substrate harder to clean, they give a very large amount of filtration. My preference in the past with my 135 was an UG filter and a large Eheim canister filter. It let the tank carry more fish. I love large schools of fish. 20-35 in a school, depending on how large the fish are. For years in my 135 gal., I kept about 3 dozen Congo Tetras (the most beautiful tetras, IMO, and the males can be over 4 inches), 2 dozen large Clown Loaches (really large), 25-30 Cardinal tetras (larger and more colorful than neons, very similar), easy to keep - actually, all 3 species are easy to keep if you have consistently good water quality. When fish that school in nature are kept in schools in a decent sized tank, their behavior can change dramatically for the better, and they're much more enjoyable to watch. I generally have some dwarf cichlids (Apistogrammas) maybe a Whiptail Cat or two, a pair of Black Angelfish, and other odds and ends. Easy to keep in a 135, and I have the same setup on a smaller scale with my 90. I have a large plastic garbage can with wheels and a submersible pump for quick water changes. I've been involved in the hobby for at least 50 years and even worked in a shop here in Austin for several months back in the 80's when I thought about opening my own shop. Almost did.
