Hydro sponge filter used in one of my aquariums.

Filters are optional if the water is kept clean but I try to change 25% to 100% of the water in each Endler home weekly. I use sponge filters in breeding tanks with no gravel. I siphon the bottom when too much waste accumulates with a clear tube and then do a water change. Corner filters with carbon and filter floss also work fairly well but I find that babies will often get trapped in them. If you use these, check them often so that babies can be released...they can die in them otherwise.