I would use floss before a sponge. No rinsing required, just toss and replace. You can get huge bags of it from Wal-Mart for like $4 :) Just make sure it's the Non-flame retardant which is chemical free.
Also instead of getting ride of the rubble have you ever tried blowing it off with a turkey baster? Works wonders for intank also. Helps dislodge detritus where it can then be removed via your filtration.
I agree with 6 fish being a lot for your tank but thats just an opinion. Coming from someone who has 2 in her 26 :) lol
Phosphates are an issue for everyone! Main contributors are the foods we feed which really can't be helped and our water source, which can be. Have the LFS check their water. Who knows maybe they are slacking on changing the filters ;)
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