Backyard Aquaponics
A place to discuss aquaponics

Looking for some help from someone with yellow perch experience. running 150 gallon FT, one pebble GB, one DWC and an 80 gallon sump. Bought 30 4-6 inch yellow perch from a local aquaculture fish farm after cycling my system. No fish deaths for first week or two but since they've been dropping consistently at one every few days. Never more than one but ive now lost about 9 of my 30. They appear to be eating my sinking pellet well. The food comes from a aquaponics guy out in CA that i trust. my numbers have all stayed exactly the same for the duration of having them. 0 ammonia, 0 nitrites, consistently good nitrate numbers, ph has stayed constant in the 7.4 range and water temp has been in the low to mid 70's throughout. I'd post a dead fish pic but ive had enough aquariums to be able to tell if theres any signs of disease. there isnt. no lesions, nothing around the gills. Are perch just prone to dying off ? i'd think if there was something obviously wrong in the water i'd be seeing mass deaths but its literally one every 3 or 4 days. Any ideas out there?

I have a few questions.

How many gallons of media in the grow bed and is there any other filtration?
Is the water salted to alleviate nitrite poisoning?
Where are the fish hanging out, near the top or at the bottom?

This really sounds like the way fish die off after having had a nitrite spike was the system cycled before the fish were added or after? If you catch one of these soon after death it might be worth doing an autopsy - you might see some indication of an internal infection. It's also possible that you have an aggressive fish but you'd probably see some signs of this. Any runoff from toxic materials or metal getting into the tank or system?

No fish were added until the system was fully cycled. ive carefully monitored my water over the last month or so since adding them and have had not nitrite or ammonia spikes. My perch are pretty shy so mostly hang out at the bottom. was floating pellet feeding them for a while and some were brave enough to come up when i was standing there but mostly stayed on the bottom. With sinking pellet they are aggressively eating it as it falls and eating any that lands on the bottom. The media bed is a 75 gallon bin filled with hydroton. Im using some manual filtration media around the pump in the sump and a filter pad to remove solids from my FT outlet. the FT is using an SLO overflow and ive been vacuuming any uncirculated waste from the nooks and corners of my FT. The FT is a 150 gallon rubbermaid oval stock tank.

I have no metal anywhere and any runoff from the wood stands into my sump is prevented by sump cover and the fact that i made the stands out of untreated Cedar. I only topoff with R/O water and any rainwater that falls into my system. IM really at a loss on the fish deaths.

Im not seeing any indication of an aggressive fish. The only thing i can think of is maybe my fish source is questionable and they came in sick.

Tell me a little bit about adding salt. ive seen other posts about it but not sure how to dose or why. thanks

I'll start out with the salt information. Salting helps prevent damage to the gills by nitrites. It does this because the chloride ion out competes the nitrite ion. Here's a short bit that helps explain it - https://www.addl.purdue.edu/newsletters/1998/spring/nitrate.shtml

I usually suggest salting to 1ppt with un-iodized salt without anti-caking agents. Sometimes you can find this in the bulk bins at the grocery store but pool salt is another option depending on how much you need. The salt also helps the fish build a slime coat and helps them with stress (so it's a good idea even if nitrites aren't a problem). At the 1ppt level the only plant affected will be strawberries.

I'm not sure what really killed these fish either. From your description they are behaving normally for yellow perch. I would try to go into their tank less often for cleaning just because of the stress on the fish. Eventually I think you would have been overstocked with this number of fish and that amount of filtration but at this point it shouldn't have been a problem and it would depend on your goal for their grow out size.

Sometimes this sort of thing can be from conditions during transportation but usually the deaths are sooner after arrival.

I'd do the salt treatment and see if that helps. I'd also up the aeration temporarily and see if that helps. Neither of these is probably directly related to the cause but they might help with stress and prevent more deaths.

Thanks Scotty, appreciate the input.

Indy,
Just to further assist - I am assuming your setup contains about 300 gallons of water based on some of the info you provided.

Based on that, to get to 1ppt for your system(assume no salt is already in the water), you would need to add about 2.4 pounds of salt.

1kg/1000L = 1ppt

lost 3 more last night. first time ive had multiples die in one day. I'm at a loss. i'll try the salt to see if it helps.

Can you post some pics of the fish? Have you inspected them? Take pics of the gills, fins, and all sides of body. What are you using for aeration?

I must have had a water quality issue. In June, out of desperation i added some charcoal filtration, the fish deaths slowed and i have not lost a fish since early July. Not sure what the cause was as my tests all showed no ammonia, no nitrites and a stable ph.

Can I double check those figures? I thought Strawberries started to suffer from salt at 3ppm and above? I could have sworn I've seen a few times now to salt to 3ppm or 3kgs of salt to 1000 litres? Perhaps I've crossed my wires somewhere along the way....

I must admit I've only ever salted my systems between 1ppm and under 2ppm (rainbow trout).

For the perch > I tried Silvers this year, they were small when added to an already cycled system and the advice I got was to feed them a lot before winter however with water temps down to 7 degree's they started dying off with no obvious signs of stress. 0 readings of Am, Ni/Na and pH between 6.2 and 6.8 so I'm convinced the cold got to them however if the OPs water temps are 21 degrees I'm at a loss as to why they'd be dying as well!

Such a shame I feel your pain after losing 50 this year in the same water that the trout thrived in for that matter

Do you have a hospital tank you could remove remaining fish and give them a 6ppm salt bath or something??

I think your calculations are wrong on the figuring out part though it can be a bit confusing. First off ppt in this context means parts per thousand not parts per trillion - just to be clear .

Your 3Kg in 1000L would be 3ppt NOT 3ppm.

1 ppt = 1 gram per 1000ml (aka 1L) OR you could also say 1Kg per 1000L.


As far as the point at which strawberries suffer - I haven't done serial dilutions to see at what point the strawberries start showing the effect of salting. I can only say that they are very sensitive to the 1 ppt added to help fish with stress so it wouldn't surprise me if lower levels caused problems but I haven't personally tried them. There have been a few people who say they have salted to 1ppt without losing the strawberries but I can't verify that they salted to the correct level - .

Wonder if you used treated water (City) for your initial fill? Seems that carbon is particularly good at removing many nasty compounds that are the result of chlorine reacting with organics in water. Not sure if YP are particularly susceptible to these....

Interesting Note: I am reading that R/O systems typically have a carbon filter as chlorine would destroy the membrane. So additional carbon filtration would only affect the initial water if it did not also come from RO...?

http://www.purewaterproducts.com/articles/carbon

Yeah, my initial fill was with city water. I did treat for chlorines and chloromines, but it could be that i just had some chemical something stressing out my fish. the deaths stopped when i lost about 70% of my initial stock and i did not lose another fish for the rest of the season. No clue why but i have to assume the charcoal helped.