Getting hatchetfish to stay at the top  9/26/06
Hello Crew
<<Hi, Tim. Tom>>
I got some hatchetfish primarily to make use of the top area of tank. However, it seems that mine prefer the middle of the tank, where traffic is already quite dense.
<<Just what you need. More traffic congestion.>>
Any idea on how to improve this situation and actually get them to stay at the top. They do go to the top for feeding and when the lights are out. I presume it's a matter of the amount of light it is comfortable with, is this correct?
<<I think you've hit on the answer to your own question, Tim.>>
How have others handled this situation, e.g. floating plants (which doesn't seem to have helped), etc.
<<Floating plants may help diffuse the light, Tim, but they'll also block the "clear shot" that Hatchetfish want when they hang out near the surface. (Little buggers don't wait for insects to hit the water, they jump out after them. No patience, I suppose.) If possible, lower the lighting levels, which I might assume you've already attempted. I would also feed them foods that don't readily sink such as Daphnia. Floating foods might condition them to stay near the top. Beyond that, I'm at a loss, like you, to offer much of a solution to this. Honestly, I've not heard of Hatchetfish "not" staying at the top of the tank. A new on me.>>
Thanks
Tim  

Hatchet Fish Question 30 Jun 2005
Hi Mr. Fenner,
<Patty>
I was hoping you'd be able to help me with this fish
question.  My hatchet fish is doing something very
strange.  For the past few weeks, it has been swimming
vertically and looks almost like it's doing a
River dance jig.  
Do you know if it is suffering some kind of ailment?
<Possibly... damage to its gas bladder... from a parasite? Maybe from too much dry food...>
Once in a blue moon, it'll flop down at the bottom of
the tank.  The first time, I thought it was dead or
dying and was about to scope him up when it flipped
back up and started doing it's jig again.  
It has been eating and seems to be aware of it's
surroundings.  I personally think it might have hit
it's head trying to jump out of the tank or something.
<Another possibility, yes>
Unfortunately, I think it's freaked out the other two
hatchets in the tank, who are swimming normally.
Appreciate any thoughts about this.  
<You might want to add another specimen or two... these are social animals. Keep your tank covered! Bob Fenner>
Thank you,
Patty

Hatchet Fish
Hey to all, Got a Q about some hatchetfish, but first a little background. I bought 4 panda Corys 8 days ago and dropped them into my quarantine tank. Three died pretty promptly (2-3 days), and #4 is still alive and well. 
Yesterday, I went back to the store and cashed in my credit for the corpses. I got one more panda and 4 marbled hatchets. The pandas are friends and two hatchets are doing their normal hover-just-below-the-surface thing. This leads to my question: the other two hatchets are hovering about 3/4 of the way down the tank (about a 10-inch tall tank). Is this normal acclimation behavior, or should I be concerned?
Data dump: 10 gallon QT, well cycled by adding water from my display. Temp 77-78F, ammonia and nitrite zero, nitrate << 10ppm. pH ~6.8. Sponge filter. 50w heater. Plastic plants and decorations. No substrate, just a little scattered gravel, covers ~10% of the bottom. I've left half of the plastic plants floating for the hatchets, and half weighed down for the Corys. Thanks a lot, Chad
<Hatchetfish are schooling fish and like to be left in groups of at least 6 or more. When kept in smaller groups they fight among themselves to establish a pecking order. In the wild their food comes from the surface, so the ones closer to the top are more dominant and probably keeping the others down. In larger schools they get tired of chasing the other fish and give up so you see them all at the surface.-Chuck> 

Hatchetfish II
Ahhhh, that makes sense. So let me ask -- should I:
(1) See if there are more of them in stock somewhere in town, and try to get a couple more, at the risk of overloading my QT tank's biofilter, (Already 4 hatchets and 2 Corys in a 10 gal QT)
-or-
(2) Wait until the first four come out of QT and then get 4-6 more? (This was my original plan.) Thanks again, Chad 
< (2)-Chuck> 

Mysterious repeated hatchet fish death
I have an ongoing mysterious death problem with common (silver) hatchet
fish.  They are in a  24 gallon 5year old community tank with congenial
tank mates. Temperature is 79 degrees, good top water agitation,
chemistry is consistently within specs (PH between 6.5-7).  I buy them
from a local store with an excellent reputation with fish maniacs.
<Hee heee! Good so far>
The problem: One by one they just quit working.  They show no signs of
damage or disease and everybody else is doing just fine. If I introduce
4 of them,  1 will die within a week or two, a month or so later another
will go down and so on, leaving 1 survivor. This process has repeated
over years (for a while I just gave up on them entirely)
Obviously I'm missing something they need.
Thanks for your time!
Peter
<Might be a lack of nutrition... for such seemingly small, inactive fish/es "gastropelecids" are pretty high metabolic animals... that eat a lot of insect larvae in the wild... need a good deal of high protein food, frequent feedings to do well in captivity... Otherwise, I fully suspect that their internal parasite fauna (all are wild-collected) are showing themselves in your mysterious losses... If you and I had a "hatchetfish farm" and were in dead earnest re keeping our herd alive, I would lace their food with Metronidazole/Flagyl AND a broad spectrum antibiotic (Tetra and HBH used to sell foods pre-made with these... but I don't know if they're still about), and feed the new arrivals for about a month once a day with same... in an effort to rid them of problems... BTW, this is a not-so-uncommon source of anomalous mortality in quite a few groups of non-cultured fish stocks... e.g. "wild" angels, dwarf South American Cichlids, Discus... Bob Fenner>