Hi, I recently got a new 55 gallon tank, but there is a slight problem. First off its not for the turtles but its more of a tank maintenence question. It was originally used as a saltwater aquarium so there are these hard shell-like pieces of something in there that I am having a very hard time getting off. I think it may be barnacles because I found some scattered in the tank and it looks almost identical. Are there any special cleaning agents or tools I can use that will be effective but not scratch and the glass and wont be harmful for whatever is going inside the tank.
ps-I am almost positive it will be used for convict cichlids, and I was wondering, if anyone has knowledge on it, does a built in overflow filter work for freshwater tanks or is it only useful for saltwater, because this tank has a built in overflow and I would like to use it instead of just leaving it to do nothing but take up space in the tank


