Sick bichir - awkward floating

[BondDouble08]

My delehzi bichir's tail end is floating up and he's having trouble swimming. He's still eating, and this came all of a sudden he was fine this morning. I heard it could possible be gas or constipation, any idea's on treatment? He's about 5.5in being fed carnivore sinking pellets, brine shrimp, blood worms, and beef heart.

-55gal
Readings--Ammonia: 0ppm Nitrite: 0ppm Nitrates: Stay between 40-20ppm

Tank Mates:

1 senegal bichir
1 black ghost knife fish
2 angels
3 ghost cats
1 tiger barb
2 mystery snails


His feces has also been floating for the last few days...

 

[BondDouble08]

Update: Ok so this is really confusing me, now the delhezi is back to normal but my senegal is now showing the same signs (hard to swim straight, bottom pointed up in the air) I have no idea how/why... this is really strange.