I keep my Phrynomantis on sphagnum with a false bottom, at least the bifasciatus are, the microps are just on sphagnum for now. Three is a PVC cap with large holes drilled in it that is utilized as a hide box by the bifasciatus. They don't seem to use it anymore. The microps have a black plastic hide box which they still very much use. The bifasciatus have a few artificial plants in their enclosure which seem appeal to them more the PVC cap. The microps have no such plants, maybe that's the reason they still use the hide box.
I feed my Phrynomantis frogs mostly fruit flies, but they also get been weevils and small crickets. They do have good appetites. I have 5 P. bifasciatus, what I believe to be two females and one male in the main enclosure and two more in quarantine, that I believe to be male. Sadly, one of the frogs in quarantine has thinned out big time. Will take both of those frogs to the vet this weekend, not sure he can do anything for it at this point. I have two P. microps, not sure of the genders of these two frogs. My big regret with them is I only bought two. They appear to be thriving just like my trio of bifasciatus.
I plan on building a rain chamber for breeding terrestrial types. It will be similar to my arboreal chamber. (see red-eye care article) I have all the material to do so, just need to find some ambition and energy.
One thing I noticed is my Phrynomantis bifasciatus have more intense color than the one in the photo. Mine are jet black and blood red.