Having both those fish myself I can say that the marine betta might as well be made of steel it is the toughest mose resilient fish I have come across! I forgot about the tank I had in the basement has no flow or lighting when I first got into this and about 2.5-3 weeks later I went down stairs to find all the fish dead but the marine betta (Pj cardinal snails, other inverts, etc) swimming around without a care in the world and 3/4 of the water evaporated. The Hippo on the other hand is not a beginner fish, well kind of. I recommend a UV sterilizer and clean water as well. I have not quarentined my current hippo or the other two I had before this one. Although the one before this one I did and he broke out in ick and died... very sad day. Im not telling you not to just make sure your QT is cycled and big enough otherwise you may be wasting your time. The marine betta hides all day and night too and only comes out when I am least expecting it.