Yes a sponge filter is fine though not my first choice - rather than using an air powered sponge I prefer an internal powerfilter (which includes sponge). Sponge filters are very efficient at removing ammonia, but do produce nitrates. But in a QT who cares?
Cycling can be done really quickly if you're prepared to sacrifice a piece of live rock to be seed material.
You have a 12 gallon with LR;inverts and think you have ich. I would NOT hypo a full blown reef. Hypo down to say 1.017, which I have seen before is NOT likely to be effective against most strains of ich, hypo down to 1.010 will kill some stuff. If I really wanted it to be free of ich I would take the fish out for two months - it's not an absolute certainty none will survive that long, but it's in the 99% + range. I would put them in as cheapo a setup as I possibly could, with a piece of old junk liverock, and hypo it down a long way OR copper them. What fish are they?
Do you have an lfs you can scrounge a few bioballs or some filter floss or something from to seed your filter. As I think I describe, for copper I have a 20 long, 200 watt heater and Fluval 4 power foam filter. I use as cheap a light as I can bodge, and bits of plastic tubing. If you seed the filter and change a bucket of water every week that is fine for 2 or 3 fish for months |