Another tip.. the other poster is right.. If you have deep tanks (like 75 gallons) they need more pressure to run a sponge filter than a 10 gallon does. What I did was put my sponge filters on top of terra cotta flower pots to prop them up closer to the surface. I got a pump rated for 80 sponge filters.. it does do that many easily, just not enough pressure for the deep tanks. Another way to prop up the filters (at least ATI ones) is to put them on a piece of 3" PVC which is standing vertically).
For both of these methods, you need to cut a hole in the side of the pot (tile snips) or pipe..
The sponge filters periodically fall off the flower pot. Once I had some loaches crawl through the tiny drain hole on top of the flower pot, but did not realize it. I put the sponge back on top, and the loaches were trapped and died. I still feel bad about that.. so leave an escape door for the fish.. Make the pot/pipe a free cave.
Other tips.. make most or all tanks bare bottom. Get an ehiem battery vacuum (you are much more likely to do a quick vac of the bottom with that than getting the syphon out when you are tired).
Make the water change as easy/automated as your budget allows. Put lots of outlets in. I have outlets wired to a timer switch for lights. If possible, heat the room, not the tanks. Put lids on all tanks (helps with evaporation). I heat the room and have lids and I don't have to run a dehumidifier, even with about 40 tanks in there, ranging from 20 galllon to 125 g..
