The mata mata does not have to swim for air, instead, he leans on the log on one side of the tank or the cypress knee (added after the picture) on the opposite side of the tank and is able to get to the surface easily that way. During the day he stays on the wood but as soon as the lights go out, he ventures into the deeper water to trap the minnows kept in there for him. It is interesting how he will lift his shell up on one side making a wall and herd the fish into a corner to eat them. He goes through about 500 minnows a month.
I am keeping the water acidic, i just added another 100ml of blackwater extract today and am keeping a close eye on the water quality. Also, i am running a powerhead on the surface of the water to give it more DO but the lower levels of the tank are rather stagnant and good mata mata conditions.
Mata mata eggs are very difficult to hatch (or they must be because no one has yet to do it) i have heard that they can stay viable for over 5 years but still not hatch according to my friend in the jacksonville zoo. good luck to who ever is trying to hatch them.