Hey fwlion, I just went over one of the journal papers I have on lungfish and it confirmed a suspicion I had that I wanted to check before I posted any thing. What it said is that it has been observed that in captivity with out the opportunity to aestivate the fish would have periods of lethargy where they would refuse food and there surfacing for air would decrease to a minimum, some times for several months. It was the assumption of this scientist that this could be a sort of aestivation type behavior. Your animal being a fresh import could have a lot to do with that. I think these fish act more like reptiles than fish and my experience with reptiles that refuse food is to leave them alone is usually the best. It is frequent that the first instinct to try to “do something” when an animal refuses food, this frequently compounds the problem. I think going to a bare tank might be helpful in making sure there are no water quality issues. I understand you want to do anything you can to make sure your fish is happy and healthy in short you are a good fish keeper.
I would urge you to just let the fish settle into what ever set up you have it in now and let “do it’s thing.” Lungfish are extremely efficient animals; this same paper notes lungfish that have stayed in aestivation for four years without serious consequence. I think once your fish has settled in you will have the classic MAL you were looking for.
Dan