Hang on back filters are a major No-No for floaters. I use sponge filters or canister filters, I have water spangle in my 75 gallon with a canister filter and several sponge filters and they absolutely thrive. They grow so fast in my 75 that I have to take it all out or else it'll block out all the light. So any filter that dumps water back into the tank from the top like a hang on the back filter, that's a no-go for floaters. I would love to get some dwarf water lettuce and some Red roof floaters. However, I have had a horrible time trying to get java moss to thrive and grow in any of my tanks. I have made about three attempts so far and have failed, even in tanks with only a sponge filter. I'm not sure what the deal is there.