Backyard Aquaponics
A place to discuss aquaponics

I have 34 Goldfish, 50 Catfish and 54 Murray Cod. I have 2 x FT one 900L other 850L, tanks are interconnected and share 4 x 500L ST and 4 x 350L GB - plenty of water. Ammonia 0, Nitrite 0, Nitrate 20-40, PH 7.2. The GF have been in the tank for over a week and the CF and MC were added4 days ago.

The GF and CF are all good with no apparent issues or problems. Yesterday afternoon got some strange behaviour from a couple of MC, darting around on the surface of the water and "flashing" their gills, then floating on their side. When I scooped them up in the fine net to look at them they "came to life" and starting scooting around the tank again. That evening found one dead MC floating on the surface, definitely no movement, mouth was closed. I don't think this was one of the "active" ones from earlier as it was a lot bigger. Next morning one more dead(again one of the big ones), and a couple of small ones doing the darting round, lying on their side thing... Thought it might have been a DO issue so added another aerator pump with 4 lines to the MC FT - total of 6 now. Have removed the fish that have been acting strange and placed them in a container with approx 20L of water and aerator stone, to which I have added 5g of sea salt (approx 6ppt?) seem to be OK at the moment but there are now 5 in 'isolation' with one looking decidedly dodgy!

Any ideas any one?

Same thing happened to my silver perch when I added them to a system that had goldfish in it already.. I suspect the goldfish were carrying something they'd built an immunity to which the SP hadn't seen before..

I salt bathed the SP at 10ppt for about an hour then put them back in the tank which I salted up to 3ppt, and that seemed to fix it.. Still not sure of the cause tho..

someone correct me if im wrong!!

arent you pushing the limits with your fish to gb ratio...
1400ltr gb with 139 fish i think your about 50 fish to much.
im only a newbi but that seems a little high for an immature system let alone an established one?

where abouts east gippsland.. im from Nyora! pm me if you dont want to put on here

cheers troy

Hey Grant, got any pictures of your system?

Yeah that is a lot of fish, they might be young now but they will be starting to grow pretty quickly and you'd better keep a close eye on your test results..

I have found that Murray Cod like having salt in the water and heaps of air. I got 30 very small ones a couple of months ago and lost half of them due to me doing stupid things with filters, but since I salted to 4ppt and have the tank boiling with air, no more deaths and they are growing very quickly.
I agree you have way too many fish and you will have a lot of deaths in a few months when they grow a bit.

I had issues with ich and goldfish and SP, it seems that the GF were carrying the desease and would show signs of it but it would not kill them, however when put in the system with the SP it spread to the SP and killed lots of them.

I would just salt the tank they are in at this point. ppt (parts per thousand) is grams per liter. If you wanted 6ppt in 20 liters is it 6 x 20 = 120grams.

Yeah when I read that I thought it was a bit odd. 5g is not much salt at all, I probably put more than that on my dinner!

Thanks for all the suggestions and advice.

I actually meant 50g not 5 but obviously still less than required, however the MC in isolation have all perked up remarkably and all seem fine. I don't have enough salt for the main MC FT but will be out tomorrow purchasing in order to salt up to 3ppt. Also added a 'fountain' in the ST with the pump supplying the MC FT(the additional 4 x GBs have no media in yet and won't be added until mid week), thinking this would also add DO as well as the 6 x air stones. So far so good with no additional casualties.

In regards to the number of fish - the GF will all be off to the dam and the additional 4 x GB are being added in the next couple of days giving 8 x 350L GBs in total. I don't expect all the MC to survive each other, or me for that matter! I am expecting my total fish weight to max at around 40kg - 50kg (I expect to harvest around the 500-600g weight). At a ratio of 3kg per 100L of GB I should be OK? (40/3 x 100 = 1333L of GB required, 50/3 x 100 = 1666L required, my completed system will have 2800L)

Troy, I am in Longford, So a fair distance from Nyora!

Thanks again for all the helpful advice.

Hey suggestion go to B's and grab a bag of Pool salt..

It cost about $8-9 for 20kg's.. Cheap..

Juergen