<10ppm is good <5ppm is ideal. Oxheart's not too bad to clean up depending a lot on how you make the mix too, e.g gelatin, cooking, flake as binder etc. They will graze along the bottom for a while which helps you out too.
It's important to feed a variety of frozen, live, and homemade foods for the fastest growth rate.
Do the biggest water changes you can too.