Lee's 5-1/2 Original Undergravel Filter, 7-1/2-Inch by 15-Inch

This was great to start out with. Soon though this caused my tank to cloud up and the ammonia levels to spike.

I use this size in my 5.5 gallon betta tank and a larger model in my 50 gallon along with a hang on back filters and the water is crystal clear. The only reason I mark them down is that their replacement cartridges are frequently ill-fitting and tough to replace. I'm not sure if there's some secret to this or if mine are just badly molded parts but every so often I have this problem. You can use them without the cartridges and as long as you have a hang on back or other filtration you'll be fine.

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It was difficult to put together. The little clear o-rings were very stubborn. In the end, it was annoying to get in and didn't really do what I wanted. Of course, I wasn't sure I wanted an undergravel filter. I'm pretty sure my opinion isn't worth much on this product. Just stretch out the o-rings before you try to fit them on. :)

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