Backyard Aquaponics
A place to discuss aquaponics

Hi to all,
I am new to this and am thankfull to Joel,Carl and Faye,
I have 30 silver perch in about 1800 litres and am still having a few probs and seeing some strange behaviour.
My fish are on the bottom of the tank, on top of each other,(no not breeding) huddling together pushing and grouping together firmly as though they are cold maybe!!
I have removed the cover and am letting the sun in, but they hate the light, prefer a dark closed tank.
Fish are 500 gms,water temp is 16-18 degrees, ammonia nil,nitrites nil,nitrates about 40, PH 7.9.
I have had them about 5 weeks and they are still not eating more than about a dozen pellets a day.
I have salted up to 4 ppt, thought I had ich, isolated 1 fish with fungus on his head and treated him in a hospital tank, plants are starting to grow, added seasol occasionally.
Also have a bio filter working the water as well as flooding the beds
Tank is polyethelene foamed sandwich construction 20 mm wall so temp stays constant, also have a heater in the tank trying to raise the temp to 20 degrees.
Does anyone have any ideas re the grouping and the not feeding
Thanks in advance
Fishdaddy

Hi Eagleworm.... welcome to the forum...

How big are the fingerlings??

I wouldn't worry too much about them "huddling" together... Siver Perch are a "schooling" fish... especially when fingerlings....

And I[ve found that they aren't extremely active (physically) when the water temp is less than about 18c.... get the temp above 20c... and it's a different story....

But they'll still school... dart along the tank and reform...

Your test readings, and the fact that you've not experienced any "spike" suggests that they're probably eating the feed... just not when you're around...

Other wise the feed would be decomposing and you would see some sort of readings... or a temporary spike...

How big are the pellets that you're feeding... are they sinking or floating pellets... and how big are the fish??

How much you should feed and what size pellet... depends on the size of the fish and total weight (biomass) of the fish....

Try breaking the feed ration into two half feeds.... morning and night... preferably the same time each day and same spot.... and see if they rise to the feed after a few days....

They may not take all the feed initially... but will clean it up later.... as long as you're not "overfeeding" them, this wont be a problem...

If you are.... then you'll see a build up of uneaten feed on the bottom... and will ultimately see a "spike" in your readings... if so don't feed the next day... and ease of the feed ration when you resume....

Yep, they like at least some shaded cover to retreat to... make sure as the twmp rises that you've got enough oxygen into the tank...

skim reading again rupe

Eaglerm, wait and see what happens when the temp hits the 20 mark. Would be interested to know that temp they were kept at before you got them.

.... yep....

Fish were at similar temp to their home. 16 deg
Fish are about 350 mm long 500 gms plate size, they were the SMALL ones that were graded out and didnt go to market.
Feed them a small handfull or about half a cup evening and morning but suck out any remaining so as not to create waste into the system, trap for new players is the waste food gets sucked into the pump and blocks the grow bed holes, gets into the beds and rots and does cause a spike in the nitrates, did a 50% water change to get it back a bit normal
They used to just cruise around the tank at all heights till last week when the weather got thundery and they hung around the return pipe, tested for nitrates and they were of the scale,80+ changed 50% and hooked up a Fluval filter to help get it back to normal.
Today they were pushing and really hugging on top of each other but seem to have settled now after the sun heated the water a bit.
I am a stockman of old and understand most animals but fish are a bit of a learning curve, guess if they are all alive then perhaps they are fine.
Maybe I look in the tank too often?
Thanks for the replies.
Gav

So, feeding at 1%... I make that a daily ration of 150gms of feed....

150 grams is the right amount, about a good cupfull, but seem to clean most of this out morning and night, some days maybe less, I will try and post a photo of the huddlers.

Fall in barometric pressure... especially a quick front coming through... or a thunder storm .... will put them right off the feed....

Usually that's followed or accompanied by a pretty quick fall in both air and water temps... same thing.... off the feed...

I usually skip a feed if that happens....

Good to hear you're aware of uneaten feed and the problems it can cause... don't worry too much about your nitrate figures though....they really wont affect your fish that much, at least not short term...

Nitrites are the one to watch... especially with uneaten feed... and obviously ammonia levels...

You sat that "they hung around the return pipe".... was this after a fairly warm day....

If so, then I suspect that your DO (dissolved oxygen) levels were getting a bit low.... warm water can't hold as much DO as colder water... in fact the difference between 30c and 20c is about 50%....

So if your water is getting up above 25+... you might need to think about having some additional means of oxygenation... maybe a airpump and a couple of airstones...

Or maybe turning the pump/volume rate up a bit... are you running continuously or on a timer basis?

The day the weather changed water temp was 20 deg the daily ambient temp about 24 deg.
We have two airstones with the largest air pump plus the DO coming in from the sump return so I think we had enough on that front.
This was the day we found the nitrates really high and figured that the fish might have been looking for cleaner water coming back through the return pipe, or maybe the temp of the water, wondered if the high nitrates is high acidic water, ( burns the eyes or gills maybe) maybe the return water was less acidic or purer after it had been through the beds.
I figured after it had been through the bed it would be slightly warmer as the beds get a bit of sun, maybe.
I originally ran timers on the hour, 15 mins pump and flood and 45 mins draining but since have gone to 15 mins flood 1 hr drain.
The plants grew better on the longer drain as they were going yellow and had wet feet.
If you see wheat or grain go yellow in the paddock it usually has had too much rain.
I think in winter I will go 15 mins flood and 1hr 15 mins drain.
I figured if I keep the rotting or day old feed out of the system had to help.
They have also been dosed with coloidial silver at 20 ppm as well as salt at about 3ppt but to keep the salt up I feel it needs to be measured,refractomer is a bit difficult due to the low rate in the eyepiece.
TDS meter is a reasonable indicator I am finding
Thanks for the assistance
Gavin



Did the water change and that improved it a lot.
Is the high nitrate something like high acid in the water?

Generally no.... but high "nitrites" can cause problems... and make the fish "burn"...

Your pH and other params seem fine.... and DO seems OK as well....

Not sure about the "colloidal silver" though... haven't heard of such a treatment...

Who recommended it and what is it supposed to achieve... I'm off googling...

Before I google away though... I'd have to say that I'd be extremely suspicious about adding it to a system with intended edible fish stock...

It is basically a "heavy" metal... and as such will have an accumulative affect in the fish flesh... especially in a recirculating system...

BRB....

Got my silvers out of season and pretty big. Didn't know if they had been weaned onto pellets just threw some in. It did take them a little time to work out that it was food. And they like to see it on the surface if they are floating pellets. Could try breaking some up. I started with 2mm pellets. But the water here was over the 20 mark so that could be playing a part. They don't like to eat much over the colder months. Any algae in your tank, they love to eat that when your not looking and any insect that makes the mistake of going for a swim. I've been trying to lay off the food until my nitrites comes down but the last week we have had thousands of crickets jumping around. They last on average 2 seconds after they hit the water.

Stop scooping the feed out - this disturbes the fish greatly. Give them less to start with.

I find that if I have been mucking about in the tank, the silvers wont take the next feed at all. Leave them alone and they take the one after fine.

eaglerm- I've been in a Colloidal Silver forum for several years, and the report there is that it can kill fish outright and also will kill the bacteria in the system. You have a bigger system than an aquarium so you probably didn't put enough in to get those results...

I was wondering if uneaten fish food can be put in the grow beds, it sounds here like it would be bad. If I suck it out of the FT with a turkey baster, I may suck fish wastes out too, aren't they beneficial to the bacteria in the gravel? Wouldn't the bacteria be able to break down the fish food as well as the fish wastes?

HB