Hmm... 1050 gph for about 100 inches of fish. 10 gph for each inch of fish. I'm sure filtration is sufficient, my experiences with bichirs and gars put them in as not very deep-bodied. Though if it does happen to get a bit dirty, I would certainly do a water change (polypterus and gars are tolerant). This is temporary anyway and before things get too serious you should have this fixed.