So if you know that the minimum size is 20 gallons, then why did you get two of them for a 10 gallon, as well as other fish????? Pictus cats can get up to 10" each, and even if you use that silly "1 inch of fish per gallon" rule, then you would still only be able to fit one, not two, and definitely not two with other fish, in a 10 gallon tank. Your pictus cats may be 'surviving' but that's probably it, they definitely aren't 'thriving' in a tank that size and it will only get worse as they get bigger. The giant danio can get about 4" and does best in a school of 6 or more.
IMO, you should return the two pictus cats and giant danio. If you like the danio, then you could get a few smaller danios like zebras. Or a small school of six smaller tetras like neons. If you absolutely have to have a catfish, you could get a couple of cory cats. They are interesting little catfish and they are always scouring the substrate for food, which helps with cleanup.