I currently have a AC50 filter on my 23G aquarium. I want to buy a canister filter and I don't know what to choose. I could buy an aquatop CF300 for 130$ which I have heard could review about it. Someone also wants to sell me his used eihem 2213 for 60$ or his 2215 for 90$. What do you think about buying a used canister filter? Which filter would suit best for my aquarium? I could also buy 2 ahem 150.