Hi, welcome to this addictive hobby!

Do read about aquarium cycling which is actually the no.1 thing to know about keeping fish yeah.

If you insist on not having a filter, make sure you have plants in the aquarium which will "cycle" the aquarium. I had a fully planted aquarium before with no filter and only 1 pump for water circulation.

You can also google for "The Walstad Method".

Have fun