I have a 55 gallon tank that has been set up for about 3 to 4 weeks. I have the Marineland 350 canister filter running on it. I cannot get my ammonia levels to go down. This is why I upgraded from a 20 to the 55. I have one Oscar one small silver dollar and an algae eater. I am a newbie and I think my pet store is full of poo poo. Can someone please help me. This fish tank is eating my pocket alive!!!! Any feed back would be appreciated.