My wife picked up 40 bluegill fingerlings and 4 catfish on friday to add to our first setup which we just finished cycling. 9 of them died on the way home, and 5 a day for the next two days. The ph is reading 7, no amonia signs and water temp is 71 degrees. Also, a few fish are showing discolored regions on their back and tailfin.
Is this mortality rate in a stressful move usual? Should I be investigating / worrying about an underlying problem that may kill them all? When I visit them, they seem happy. They are usually grouped on the sunlight side of the tank and eat small coy & goldfish pellets that i'm crushing for them
Transporting fish can be really hard on them. Especially if they were stressed out for a while before being packaged for transport and if they spent too long in transport or didn't have enough oxygen, that could explain the deaths in transit. Then it is not uncommon after a bad transport for some fish not to survive long and die later.
I'm not sure what to tell you other than keep an eye on water quality and make sure they have enough aeration and hopefully the strong ones will survive for you.
i have a 1/8th inch aeration hole in the growbead that drains down into the 300 gallon tank. A 700 gph pump is pushing through a bell cyphon cycle about every 15 minutes. After a cycle there is ~ 2 minutes before the level where the 1/8" trickle drain is reached again. Would you recommend i create more somehow? tapping into the pump out before it gets to the grow bed and returning some?
add an air pump and air stones
Keep a good eye on your water tests. You should have very little ammonia like no more than .25 ppm with 0 nitrite. If you've got much nitrite, that's probably your problem and if it is you should do partial water changes until your levels are good. Since they are feeding, you may have enough O2. My fish were straight out of a pond and even after my cycling issues were over a few bluegill died, along and along, one or two at a time. I think those straggling deaths were fish that didn't adapt to tank culture. Altogether, I think I lost 30-50 out of 200 bluegill and the deaths stopped after about a month. Good luck.
AIR pump and air stones are the normal method of additional aeration but if you have alot of exess pump flow a spray bar over the fish tank can help but if you need all the flow to kick your siphon over, you will definitely want an air pump.
It's very tempting to feed, if not overfeed new arrivals. As mentioned above, where were ammonia and nitrite levels?
You mentioned your pH was 7, any idea where the pH was at the source for the little guys? Did you do a slow transition, mixing small amounts of your system water to the new fish water? pH shock can be a real killer. Crank up the DO and depending on what your system will tolerate (plants and current salinity), a little salt can help with the stress as well.
Much of the trauma can come on the pre-packaging side and if the supplier didn't bag the fish with pure oxygen, then a long drive or too many fish in too small a bag would really take a toll. Seeing as you said 9 were dead on arrival I expect most of the problem is from before you got the fish home.
Just be careful with bluegill not to salt too high since they are supposed to tolerate salt levels above 5 ppt well.
Channel Catfish take salt even less well. I don't salt over 3 ppt with the catfish normally.
But yes, I like to salt a system if I know I'm going to be handling the fish heavily or for transport or in a new system where stressed fish will be getting introduced. Salt between 1-2 ppt is a good tonic to help with stress and slime coat. 3 ppt is appropriate for illness or injury. Just make sure you have good aeration since adding salt will decrease the amount of oxygen the water will hold a little bit.