I forgot to mention one thing about the 4 gallon Designer tank from All-Glass. The tanks doesn't easily adapt to a HOB filter. It comes with an undergravel filter, but I didn't use that. I used a small internal filter, Duetto DJ50 from Marineland, that seemed to be the easiest. If you wanted to use a HOB or cannister, you would have to make a hole in the hood. It would be easy to enlarge the hole for a cannister, but a HOB filter would take more work, but it could be done.