I have a 20 gallon w/3 live plants, 2 fake plants and 2 decorations. I now have acquired since November 5 neon tetras; 2 otto cinclus; 2 platies; 3 albino cories. All of these fish do not exceed 2-3". I had to have the cories, but I want to get 2 guppies, then I'm done. Is that ok?