The only aquarium I ever had containd two goldfish that I rescued from my workplace. Someone just had them in a fishbowl, letting the water get all dirty...solid yellow and smelly.
What I didn't know then is that goldfish are pretty dirty in terms of fouling an aquarium. I put them in a 10-gallon aquarium with a filter, but I had to clean it thoroughly every week...or was it 2 weeks? It was quite often. I'd actually take the fish out and drain the tank and put in fresh water.
I had those fish for at least five years, then they died one by one. It was sad. My husband and I actually cried. Of course, we're suckers for every living thing.
Unfortunately, I've never wanted to have an aquarium again even though I now know that other fish would not require such constant tank cleaning!
Oh...my fishes' names were Gigabyte and SCSI (pronounced Scuzzy). My husband is a computer geek. : )