my 40 gallon has quite a bit of algae...so I went out yesterday and purchased 5 ottos to help clean it up....my tank has a betta....green neons....shrimp and nerites....I have now read that a betta is not a suitable tankmate and the substrate is too sharp...I used to be so much better at doing my homework. Sigh. I am really not worried too much with my betta....as he is fairly chill (used to coexist with corycats) and is peaceful in his tank now. My concern is the substrate. Can I cover my Eco Complete with some black gravel??? The tank is heavily planted but many open areas exist where my ottos could hurt themselves. The tank has been up and running since April btw. Thanks in advance. Also please note the ottos are in a quarantine tank right now so I have time to figure this out.