Plants for BGK

[dkpate]

I have one single Black Ghost Knifefish and I was wondering if it would be okay to plant low light plants only, since he is a noctournal fish and HATES light. Right now he is in a 20G tank where I am struggling to get the ammonia down because I did not do a fishless cycle . (I was told that if I used Hornwort, it would help being the levels down, true?) I am going to be starting a fishless cycle on his new tank today (which is 60G) and I just read that crypt plants could be planted in the low light (for the 60G). I hardly EVER turn his overhead lights on, (the only reason I am doing it now is to try and grow algae to help with the ammonia, was told that too), and usually just let sunlight in during the day. Where can I buy crypt plants or any other low light plants, and whatever needs to be bought to maintain them? The pet store I bought the fish from only had 2 different kinds of plants, (I bought them), and they seem to be doing fine for now and haven't had any part of them die in a week. Any help is appreciated! Thanks!