I bought a house last year that came with an outdoor pond. Yay! But its been completely neglected for probably years so it needs a lot of TLC to be pretty again. So here's some basic information.

-450g based on dimensions of 8 x 5 x 1.5

-Large creek rocks embedded all around the perimeter and several feet in any direction means enlarging in any direction would be a much bigger undertaking than I can handle right now.

-Currently filled with tree leaves and the accompanying muck

-no fish

-added some body plant root bundles but no idea if they're growing yet or will

-during summer is completely shaded

Plans for the summer are to de-muck it so it's habitable for fish and trim the trees all around it so it can get some sun and the plants grow properly. Right now I have a small waterfall I put in to add some circulation, but the pump can't be connected to a filter. I added it last year, but when I went to connect it to a filter this year I realized it can't be connected to one so I need to get some kind of filtration going on it. Filtration will have to be either internal or something that can sit on the surface though, and preferably cheap as I'm not working right now and my reef tank eats most of my fishie related budget.

Eventual goal is habitation by goldfish as I understand its too small for more than one or two koi which wouldn't be that much fun.

Suggestions?