Blackfin Catfish attrition

Question
We recently set up a 10 gallon freshwater aquarium with a heater. Temp
seems good. Population now consists of 3 tetras and one puffer fish since the
demise this morning of our second black fin catfish in as many weeks. We
thought the first death was a fluke, but noticed the second exhibited similar
behavior - Swimming in a close circular motion from top of tank to bottom.
Each catfish has had its whisker show damage after a few days, though we've
never seen how it occurs.  My suspicion is the heater generating some sort of
radiation that's disruptive to this particular fish but I could be full of crap.
The swimming motion is always in close proximity to the end with the heater.  
Let me know your thoughts and if you need more info.  Thanks!  -John

Answer
I doubt the problem has anything to do with the heater. The other fish are doing well. The cats are simply near it because the heat makes them feel better. Like if you sat in a hot spa for a pulled sholder. Makes you feel ok but not solve the problem.
I suspect the cats have something called  "SWIM BLADDER DISEASE". It is a bacterial condition that deflates the air bladder inside. The Air Bladder is what the fish inflates/ deflates at will to stay upright. It always causes swimming problems. Mollies are well known to get this.>>>>>>>There is no remedy fot it.<<<<<< Many times it can be found in an entire brood of young. Where ever you bought them there are more in that tank at the store with this condition. I am not 100% about this but I'd place a bet on it. Also, the whiskers were damaged from the fishes frantic swimming to stay upright. The fish has to swim fast or else go upside down. It can't breathe upside down. The faster it swims the worse it gets, then more water gets in the air bladder and death comes. This is in no way related to breathing.
 I'd get a different species of catfish.....
Suggestion is.....ANGELICA CATFISH...peaceful, shiny silver with blacK dots, real real long whiskers that go back from snout to tail. Get 4" to 5". About $5 to $7 each. Unlike other cats these guys swim in the open. They do NOT eat rotting food on the bottom. A common misjudgement is that catfish forage the bottom for food and eat the rotting garbage. No. No fish like to eat spoiled food or garbage. Catfish just like to find their food there. ANGELICA's though will eat from the surface. and anywhere else. A COOL FISH.