i have a 125g with two silver aro's both are 8"s, and a heater set at 78-82F dont have gravel or sand and running a emperror400, some of you know who owns aro's know that they make a lot of droppings, and also i do 25% water change every other week. well the other day i saw like a white gel or fungus looking on their droppings, is this normal? because the aro's looks fine to me, how can i prevent this from growing on their droppings again, anybody got advice lmk asap thanks.