Backyard Aquaponics
A place to discuss aquaponics

Unfortunately over the weekend I've lost 2/3 of my SPs.

Murphy's law has it this was the same time the forum started acting up, but I just found a way to get into the forum, so I'm hoping someone can help.

Basically, not too much has changed in my system since my fish were happy and healthy. 3 main things have happened in the last week or so.

• Two weeks ago - I fixed my overflow on the FT in place, as any little bump would make the silicone surrounding it leak. It had got that bad that there was a constant leak, causing a fairly significant water loss. To fix this, my plumber friend gave me some 2-part epoxy stuff, that he assured me was non-toxic as they use it for applications involving drinking water. To apply it, I drained the tank a little to make sure where I was working with the unset epoxy was dry, and kept it that way until it had set. During this time (about 4 hours), I had an aerator going, and the fish seemed fine throughout the process.
  
• Two weeks ago - Water top up mishap. One of my irrigation pipes came away from a GB, causing a couple of hundred litres of water to escape from my system (500L FT with 500L ST). I always top up into the sump tank, and usually use tank water if available, but on this occasion, my tank was almost dry so I was using tap-water. I planned to only introduce about hundred litres each time over a few days to gradually top it up, but forget the hose was running, and accidentally refilled the whole system whilst running, so it may have introduced a few hundred litres of mains water.
  
• One week ago - New food. I had run out of food, so went to use the 2nd container I had. Alas, it had gone mouldy, so I didn't dare use it. Instead, I sourced some food from my fish supplier. It looks like the same Ridley 2mm stuff I've used before, and didn't appear to be contaminated, even thought it might have been the bottom of a big ~20kg bag (that's what it came in).

Over the weekend since Friday morning, my smallest silvers started dying. They weren't floating, but lying on the bottom of the tank with mouths open. They looked ok - no real blotches or visible signs of disease. I stopped feeding immediately.

On Saturday I lost a few more silvers - again, the smallest ones in the tank, so possibly the most vulnerable I imagine? I introduced some duckweed, thinking it might provide some natural food for those that might be hungry, with no risk of it going off if it went uneaten.

On Sunday I lost a few more, again the msallest left. All up this was now about 2/3 of my fish. I was in a state of despair, and couldn't get the forum to work to identify a course of action to take. The only thing I could think of was salting the tank. Hence, I placed about 1.5kg of pure salt well diluted in 10L of water into the 500L FT. I figured this should take it up to around 3ppt, hoping I got the calculation and amount needed right. I had important business to do, so couldn't hang around to monitor the fish.

I just checked this morning, and no fish losses. My fingers are crossed that the ordeal might be over. Now I'm worried about the cause of the problem, and want to ensure everything is good again. A main concern is the food. I haven't fed them since Saturday, and I'm worried the food I have may be contaminated. If it is, I work all day, and can't have any more time off to source some more. How do I test the food I have? I figure it's not worth risking it, and would rather get more, but logistics makes it almost impossible. How long can I go without feeding my remaing 7 or so fish (2 at 15cm, 1 at 12cm and a few at about 8cm)? Will they survive on duckweed instead of starving until I source more food?

Hopefully I've provided enough info to allow some of you gurus to provide some of your insight, and prevent me from losing more fish.

Unfortunately I have discovered that witha true HSM such as you are suffering, the fish you eventually lost were possibly doomed from the start, they just took a while to drop off.
Firstly, My concerns would be for the epoxy you used. It may be safe for human consumption, but perhaps some of the agents when wet are bad. it's possibly you didn't let it cure for long enough, and then didn't rinse the fitting enough.
flushing and perhaps overflowing the system with town water may be an issue. Again, town water is safe for human consumption, but fish don't like it. Check with your water board to see if they use Chloramine. I top up with tap water all the time and have never lost an SP.
Being two weeks ago, I'm doubtful that these are the main causes.
This leaves the food. as far as toxicity goes, I'd be very alarmed if fish food was toxic to fish.
tell me, are the pellets the same size? You say you lost the smallest fish. I usually find it's the bigger fish who die, as they require more oxygen, absorb more ammonia, eat more food etc...
I'd be concerned if the pellets were a different size, that your fish were choking on their dinner.
Other than that I really have NFI... there are few ppl here on the forum who can know for certain why fish die. Even our most prominant members have difficulty at times.

If you have a small quartine system that you can move a fish as a test. Feeds when moldy can be extremely toxic. Which is why some states do not allow deer feeders. Its not so much of the sportsmanship as it is toxic when moldy. Moldy feed will make deer a little sick but will kill an entire turkey flock. Just wondering if temperature shock may have been the culprit on the fish. Also the vinyl from hose pipes when left in the sun puts off toxins but I doubt that. But a large dose of cold water can do them in.

I'd say a nitrite spike. Adding so much tap water may have have upset the bacteria.

The salt reduces the toxicity of the nitrite, so thats probably why they stopped dying.

Water test results?

Thanks guys.

Forgot to mention water test results:

Ammonia - 0
PH - 6.8
Nitrites - 0
Nitrates - 2

The only other things I forgot to mention, now that I think about it some more. First, I noticed a few days a go they didn't seem hungry - usually they're almost striking the surface when I throw the feed in. Also, a few were occasionally quickly flipping on their side, flashing they're "silverness" as they swam.

FWIW, the remaining fish look and are acting fine, but so were the others. I'll investigate the epoxy when I get home. The tap water I can't do anything about now.

As for the food, I'd really like to replace this as it's cheap enough to remove from the equation - the only problem as mentioned is logistics. No idea where to get it from before this weekends, and even then I'm unsure where to go. I'm reluctant to get more from my fish supplier, as the stuff I have now that may be dodgy came from him. I'll post a request to buy some from hopefully a local APer and see how I go.

What's your water temp Ryan... and any idea what it was when the fish started dying??

Dunno what the water temp is, but it's been fairly normal up here in Brisbane (mid to high 20s during the day, not sure how cold at night).

I started losing fish last Thursday IIRC.

Contact Ridleys... they up your way....

Did you guys get any rain during/after the dust storm arrived up there??... Any chance of run off into the tanks...

I suspect, from the fish laying on the bottom dead, with mouths open... that they'd been dead for a day or two...

Ridleys are a PITA. I've tried calling them a couple of times, get fobbed off, directed to answering machines and never called back. All the produce suppliers around here don't have kind words for them either!

No run off after the dust.

The fish were dead for 24 hours max. Funny thing is, there was only ever one floater.

You might not be able to do much about the mains water that was added at this point but it would be good to know what your mains water is treated with. Chlorine will have a very temporary effect while Chloramine tends to be more problematic long term.

4 more losses this morning - none last night, so this all happened overnight.

I've cleaned out the residue of uneaten food/poo (I imagine that's what it is) off the bottom. Mind you, there was no more than there has been over the last 12 months when the fish were fine, so don't think this is the cause.

The only real thing I can suspect now is the putty I used to fix the overflow pipe to the corrugated iron FT, as that's the only recent change to the system. I'm confident it's not the tap water. Again, all the larger fish are still ok, and it seems the smaller the fish, the earlier the death.

If it is the putty, I'm screwed. It sets that hard, that I don't think I can remove it. Hence, I'd probably be up for a new tank, and this would be very expensive and enthusiasm sapping.

BTW - any idea how I could affix the 50mm drainage pipe to the corrugated iron tank other than using putty? I tried sikaflex in the past, but every time I slightly move the overflow pipe to lift the lid on the ST, it starts leaking.

Also - will silvers live on just duckweed? I'm still not game to add food, and they don't seem real hungry anyway. I added a heap of duckweed a few days ago (almost enough to cover the tank). It seems they're eating a bit of it, but not heaps.

Can you seal the putty with an epoxy paint?

Were you doing regular water tests through all this stuff that happened, especially shortly after the huge water change?

If the big water change upset something, it really could have taken a while for it to weaken the smaller fish enough to die off. What were your pH readings before the water change, and after. What about ammonia and nitrite? And of course the primary killer of the smallest silver perch seems to be temperature.

If the water change caused a hard sudden shift of pH, then that could have a residual effect on fish. Also, if the water change killed off a large amount of the bacteria colony either with a pH shift or with water treatment chemicals, then there could have been ammonia and/or nitrite spikes after the water change which might not have killed the fish instantly but can definitely stress them and weaken their immune systems leaving them prone to diseases that might kill them shortly thereafter. Add in possibly low quality feed and/or solids build up in the tank contributing to possible water quality problems, it might not be any one thing that is killing the fish, just a combination of things.

More info about water quality, normal system pH and the mains water pH as well as treatment chemicals and any warning labels on the putty might help isolate the problem for future reference.

You mention finding dead fish in the morning, are you finding dead fish more often in the morning than later in the day? If so, I might also ask about dissolved oxygen. Does your system run 24/7 or do you shut down at night. Is there any supplemental aeration?

Everything seems to have stabilised now. I ended up with 7 SPs left. 2 were from the original lot I had that survived the first catastrophe, and 5 are fro mthe more recent lot.

They all seem to be doing fine, but I have noticed they're not eating as much as before the HSM. I wonder if this is a legacy issue, or they're eating the duckweed that I added to the FT to try and help stabilise things and provide food whilst I had ceased feeding them? The duckweed seems to be disappearing a bit, but not as fast as I would have expected. Maybe it's growing almost as fast as they're eating, but I cna't confirm this.

Anyway, I'm ready to jump back on the horse, so to speak, and will be adding some more fish as soon as I can get them. I'm keen to go with some jades this time, just to mix things up a bit.

Water test results? Temperatures?