If you bury the rhizome of the anubius it will rot. They need to be tied to something or weighted down.
I have an eclipse 6 gal - which has very low light & my crypts are doing well.
Both those plants & the java ferns are low light plants.
I do dose excel, seacheme comprehensive & use fert tabs.
I love gardening & see how well terrestrial plants do when fertilized so figure aquatic plants will do better w/ a bit of food also.
The substrate is flourite.
I have a betta & 2 snails - so no advice on the fish!