Keep reading all you can on your dwarf frog, so that you can learn all about its needs. (There are a few frog forums, like this one, out there, like frogforum.net or talkto.thefrog.org, and if you do an internet search, there are a number of species-specific sites.)
One dominant view among hobbyists is to avoid species mixing of any kind. (I won't rehash the arguments; they're all over this site, and a simple search will pull up some of the debates on that front.)
Here is what I have to say about it, even though it may offend some people:
1.) quarintine your frog to ensure that it is healthy before even thinking about introducing it to a tank of fish. (Sounds like you've begun this.)
2.) If you have fish that are small enough to fit into its mouth and that you would like to keep alive, do not put the frog into your fishtank.
3.) If you have plant coverage, or other hidey places, AND a community of small-ish, non-aggressive fish, you might try (and here is where I will offend some) to introduce the frog after his quarantine.
4.) The hypostomus (is that the biggest fish in your tank?) might try to "suck" on the frog if he is underfed. (I had a similar experience with a pleco, and from then on, made sure to offer plenty of sinking algae pellets. It has not happened again.)
Beyond that, I might need to know the rest of the fish species in the tank to give any advice on their demeanor and the likelihood that they will attack.
I posted this because I genuinely feel that, if one is responsible and observant with the tank, dwarf frogs really can make a wonderful addition to a fishtank. (I have three that I added to my tank in ~2003, and they are living among cherry barbs and other peaceful fish, and they have been a joy.) Before you act on my advice, search for some of the anti-species-mixing arguments, as they are valid and worth considering. (I'm sure a few people will chime in after this posting to represent their side.)
I will also add the disclaimer that, in defending the practice of adding dwarf frogs to fishtanks, I do not mean that any species can be mixed with any other in any environment. (As I said, the anti-mixing camp has some very valid arguments.)
I just figured that, since you are new to dwarf frogs, it might be worthwhile to look into various ways of housing them, and decide what you think works best, for the animals and for yourself.
(To others who have read this and are on the other side of the debate, please remember that I mean no offense.
)
Enjoy your tiny darlings.
