Go easy on feeding in a20g I feed my nem's twice tops and small amounts they also get food from light
buy some test kits and find out forypur self what your parameters are I'm not sure shat they test for at lfs . I doubt water changes daily is beneficial to your system especially in a small tank by rights you should be doing 2g a week so not to stress everything out . Gsp, Kenya and most zoa's are pretty much indistructable