When I first started keeping fish I had a bad experience with having a frog. My 5 gallon I bought from Wal Mart barely worked and did not move the water. I added a betta and a frog but they both died on the same day about a month later. They never fought but I did notice the frog spending much of his time at the surface. I think there is a chance that suffocation played a role in their deaths. They were both very sluggish but showed no signs of discoloration or stress.
I have since bought a new filter and an air pump. I have three male guppies in the tank who get along famously. Would it be okay to add an African dwarf frog to this mix? Would that exceed the biological load? If not, could I add two more guppies maybe?
For reference, I clean the gravel and replace 25% of the water about every five days, no longer than a week. I wouldn't mind doing this more often as I find it to be fun.