True in t5heory I think, I have a pond sterillizer on my pond outside, it is not very effective, and was bought as quite oversized! I have a slow flow through it currently and it still is not very effective. For your aqaurium, I would think that one that was designed for it would be better, just my thoughts...I wish I could use a pond one, much cheaper, but same old story, you get what you pay for!!
Bill