I currently have a 30 gallon planted tank and was hoping for some suggestions as to what other animals I could add to it. The tank is cold-water, though here in Orlando it never gets below the AC setting of 72, and has a sand bottom. I currently have one yellow applesnail and 3 hardy goldfish. The goldfish were originally just to cycle the tank, but they didn't die and I had gotten attached by that point. There are lots of river stones and driftwood in the tank for something to hide in as well. I would prefer something that could "earn its keep" by helping to keep the tank clean. Any suggestions you can offer would be greatly appreciated! Thanks!