Backyard Aquaponics
A place to discuss aquaponics

Hi All - hoping you can help. I'm really new at this so forgive me if this question has been asked and answered on the forum before.

A bit of background:
Weve had the system set up 5 weeks ago and weve got 1 x 1000L with one grow bed attached (tank 1) and then another 1 x 1000L tank with two grow beds attached (tank 2).

We purchased 30 silver perch - 10 of the bigger ones (8-10cm) are in tank 1 and 20 of the smaller ones (3-5cm) are in tank 2.

Tank 1's ph is about 7.8 zero levels of ammonia, nitrites are about 2.5 ppm and nitrates are about 5ppm.
Tank 2's ph is about 7.8, zero levels of ammonia, nitrites and nitrates.

the temp in both tanks are within a comfortable level for silver perch (as I understand it) and only differ by about 1 degree between them. At about 7am in the morning both tanks are around 20 degrees and by the afternoon 5pm the temp gauge reading about 26/27 degrees (depending on the day).

Tank 1 gets more sun than tank 2 which is partially covered on both sides by grow beds, but both tanks have timber slated covers with fly screen on the back so no debris can get in. The water in both tanks is clear. There is a fair bit of biofilm already in tank 1 whereas tank 2 only has a little.

the fish in tank 1 are going great and eating really well but the fish in tank 2 have dramatically reduced their feeding to almost non existant over the past two weeks. I thought it might have been a spike in ammonia or nitrites so I stopped feeding and ran the pump full time but their feeding hasn't come good even though there are no detectable levels of ammonia,nitrites or nitrates for about 5 days now. I've salted the water as well to make them a bit more comfortable and tried just throwing a few pellets in but they don't seem at all interested.

we haven't lost any fish so far and happy to be patient but was starting to worry that this was more than the fish just "being off the feed" so to speak.

any ideas?? Something I'm missing?

Welcome to the forum

What are you feeding your silver perch eg brand/size of pellet/protein content? Are you using floating pellets?

When you say the fingerlings in tank 2 aren't eating, do you mean whilst you stand and watch? Silver perch fingerlings can be extremely shy - the shiest, most anxious scaredy fish I have ever kept.

My silver perch fingerlings never ate when I was hovering over the tank watching. Once they get a bit bigger their confidence grows.

Try this - assuming your pellets are the floating type, throw in some feed and leave them to it. Come back in say 20 mins - is the food still floating around or have they stealthily eaten it whilst you were away (the tendancy of small perch)

thanks for responding - yeah we are using floating pellets although I do have some sinking stuff as well. The brand etc I'm not sure about but the fingerlings in Tank 2 happily ate those same floating pellets with no problems for 3 weeks and have now gone off the feed all together for the past 2 weeks.

The feed is kept in a screw lid container and its the only stuff I've fed them from day one. Tank 1 fingerlings are eating from the same container of feed and don't have any issues.

I've been trying a teaspoon of feed in the tank in the last couple of days to see if they will eat it. I've tried leaving the pellets in the tank for a few hours and I've also left it in all day - like 8 hours while i'm at work and the whole lot is still sitting on the surface when I get home. I don't open the covers at all on either tank when feeding them - I just slip the feed in under the grow beds because the cover doesn't reach that far. I would have expected them to eat the pellets when I wasn't at home but still nothing.

I've tried feeding them in the morning - the fish in Tank 1 like a morning feed but I've also tried introducing feed just in the afternoon for the fingerlings in Tank 2 in case they prefer a different time but again nothing.

The weird part is that the fingerlings in Tank 2 were much braver than my bigger ones in Tank 1 and started feeding on their second day in the tank. It just all seems to have gone a bit pear shaped. I just don't want to miss something and then all my fish end up dying.

thanks for your help

You say that they ate at the start then stopped? If so maybe they dont like the feed you are using or it is off
Just guessing here

Relax

I don't think your fish are in danger of starving to death. Keep in mind that unlike us, they are cold blooded animals, with less energy requirements - they adjust their metabolism to the amount of feed they are getting so may perhaps be a little less active if not eating for an extended period.

Some folks here will leave their fish unfed for a week or two when they go on holiday etc, and the fish are fine. In fact this is a far safer scenario than leaving your fish in the hands of a friend or family member who are often tempted to over feed.

Assuming all your other water parameters are indeed safe as you've described, my hunch is your fish will go back onto the feed again, if they've eaten it before.. just might have to be patient for a bit

What sized pellet are you feeding? If it's too big, sometimes fingerlings will wait for it to become aged and very water logged so its easier for them to munch at

Do you have sufficient water turnover and oxygenation of the water?

Yeh agreed, worth checking that for sure

If I were you I would also consider trying another brand of feed.

Is your fish food just stuff bought from a pet shop, or is it proper, formulated aquaculture feed?

Crisis averted they started eating again this afternoon! Murphy's law isn't it. thanks very much everyone for their thoughts/suggestions and help - much appreciated.