I inherited three surviving
ADF's from my mother - they were starving to death in her 40 community tank.
ADF's should not be in a tank higher than 18" (they may be able to come up for air in a higher tank but will tire out after a long time of having to do it).
ADF's cannot compete with community fish for food... that's why the rest of my mother's
ADF's died, the community fish ate the blood worms before they could get a belly full. I keep the
ADF's in a 5.5 gallon tank with a male betta, lots and lots of rock caves and so many artificial plants the tank looks crowded. The
ADF's like to use the plants as resting places and as stepping stones to get up to the top for air.
Another possible problem is the cories. I ended up having to get them the 5.5 when I needed the 20 for a
QT tank. I had initially tried putting them in a 10 with my son's male betta and cories and the cories are just such busy little creatures that they stressing the frogs out.. the frogs never had a chance to rest.
ADF's are best kept by themselves. You can attempt keeping them in a community tank (without bottom dwellers) but only if you want to put in the time and effort that it takes to feed them. Some
ADF keepers have trained the frogs to be hand fed, others use turkey basters to squirt the food right under their noses while keeping the rest of the fish at bay with a small net. Too time consuming for me - I find the 5.5 is the perfect size for them and the betta doesn't eat enough to take that much away from the frogs.
Sorry for your losses...
ADF's aren't the easiest to keep. I did a lot of research to take care of these ones and so far, so good - we've had them about six months now, my mother had them for a few weeks before that.
Oh, they are also escape artists -- top of the tank needs to be SEALED off -- even the tiniest gap. I used plastic crafter's mesh cut to fit like a glove around everything and electrician's tape to secure it to the top of the hood. On the plus side, plastic crafter's mesh comes in about a thousand colours so you can get one that will blend right in and won't be noticeable at all.