Backyard Aquaponics
A place to discuss aquaponics

I feel for you (I was losing 10 silver perch a day at one stage). Your best bet is to listen to the advice of the other more seasoned members, I did and eventually the death rate fell and disappeared.

Hvae you thought that the cobination of ammonia and high pH are killing your goldfish.

Remember that the higher that pH the ammonia becomes the "activated" type which damages the gills of the fish. 8.4 pH compared to most of the systems that are running at 7 or below would be enough to damage you goldfish.

Just my thoughts but may be valid

Nick - you are close to the mark in my opinion. Val, we need a temp. Even at 20 degrees C, .25 TAN (total ammonia nitrate) will be toxic at 8.4pH.

nick, nice use of copy paste (exactly the same explanation as offered in my thread) - I was wondering where you pulled the 8.4 from in my thread

sorry actually posted it in the wrong thread and could not figure out how to delete it after I moved it here, so if one of the mods would like to do it feel free

I am having same issue, 3 of 10 I have added to test my system have died. They are the feeder fish and were skinny things when I put them in and they have been pretty much been eating non stop since and have turned into fat little fish. I have not been feeding them, they have been grazing on sides of tank and duckweed some. Water tests look real good. The ones dead looked fine, the rest seem very happy and perky.

Is it possible for a fish to eat itself to death?

Timberdoodle

When you say fat, do the fish look swollen? Check their scales, are they sticking out slightly? Maybe like a pinecone?

Skinny to fat in such a short time doesn't sound good, if the discription above fits, they might have dropsy.

Below is a link to common fish ailments, the first pic is of dropsy in an advanced state.

http://www.answers.com/topic/list-of-aquarium-diseases

Dropsy is swelling due to internal hemorrhage. It may be caused by parasite, infection, or blockage of internal organs. It is fatal more often than not.

If the above description fits I would quarantine those fish ASAP, rather than risk my system being contaminated. IMHO

Thanks for the link, that looks like a real good reference site to save for help with fish issues.
I don't think that is the issue here- fat in this case means they now looked like regular goldfish compared to their previous state, the other symptoms for dropsy are not indicated.

Also, I lost a fish per day on days 3,4 and 5 after adding to tank. Tank is about 700 gallons.

Timberdoodle

What exactly are your water params? Amonia, nitrate, nitrite, ph, and temp? What flow rate is your pump?