Backyard Aquaponics
A place to discuss aquaponics

Regarding the zinc from un-coated rainwater tanks, the zinc may also be coming off a "tin" roof. Others on this forum are using rainwater from "tin" roofs. However, I am reluctant to do so. My wife experimented with gambusia in an aquarium, and filled it with rainwater. Overnight the fish died, their skin peeling off. The same fish (maybe brothers and sisters!!) could handle a complete change of water using scheme water straight from the tap. The rainwater is our household water, collected off zincalume roofs that were about 5 years old , and stored in a lined zincalume tank.

I have more confidence in this morning's test results:
pH 7.4-7.6
NH3 0.25 ppm (possibly as high as 0.5 but I'm sure the closer match was 0.25)
NO2 0 ppm
NO3 2.5 ppm (inferred)
Temp 22 C

Goldfish are back off the bottom and looking healthier.

Will monitor today and possibly do a water change tomorrow if the situation deteriorates.

Cheers
James.

I'd still salt to at least 1ppt ... as a preventative tonic....

Any sign of fungal infection... i.e. fin rot.... do another water change and whack the salt to 3ppt...

I think salting the water sounds like an excellent strategy, as well as adding some CaSO4 or MgSO4 to up the hardness.

If I lose any more fish I'll photograph them and post here.

We've got something like 43 degrees here today so the water temp is probably hovering around 28-29... Fingers crossed...

Keep your tank turning over and your aeration up Jimmy... fish are probably already stressed...

Yep, this whole heatwave I've had it on continuous flood between 11am and 5pm (flood 15 & drain 30 at other times). This keeps the water turning over. However, I still need a Dissolved Oxygen test-kit to see if I need supplementary aeration. I guess that's another thing for me to buy from the aquarium shop tomorrow...

I'm very pleased to be learning all of this stuff with only 10 goldfish on the line, rather than losing 50+ silver perch as happened last time... (Not that I condone the reckless destruction of goldfish - but in the interests of learning how to operate a proper system, and what can go wrong, especially in these extreme conditions...)

P.S. Thanks for all your help! And patience with a slow learner...

Okay, we lost another fish in the 43-degree heat yesterday. I was at work but my wife tells me it was gulping at the surface. This is symptomatic of low DO so I'm off to buy a DO test-kit if I can find one.

I took some photos of the fish when I pulled it out of the tank late last night and it looked like there was something wrong with the scales on its sides - they seemed sort of "dull" in patches, as though the slimy gloss had been corroded or something. This is the best photo of the bunch but it doesn't show the dullness of the scales.

Found another one gulping for air this morning. Tried to oxygenate it by sticking it under the inflow pipe - almost obliterated it with the flow.

Noticed that there was some scale discolouration like the previous one last night. Removed the fish and placed it in a bowl with about 2 ppt salt (not sure what sort of salt it is - it's all we had and it's probably the wrong stuff). I think we'll lose this little guy too, but I'll take him to an aquarium shop and hopefully they can tell me what the discolouration might mean.



Strangely, I spotted a fish swimming around very quickly and happily in one of the other ponds. So far all of the FISH deaths (apart from the yabby) have been in the sump so I wonder if that is significant?
Differences between sump and other ponds:
- sump has no water plants
- water level in sump fluctuates by about +/- 40%
- most water disturbance (due to inflows and swirling action caused by diverted pump water)
- different material - sump is galv with a custom poly liner while the other ponds are those green poly 500L things from the big hardware shop.

Sump is obviously much smaller/shallower than the green bins James...

Water temp in the sump will probably be much higher than the fish tanks...

Oxygen decreases markedly with higher temps.... to a point of near zero....

I wouldn't bother with a DO test kit... I'd suggest... shade your sump, buy an aerator and apply a couple of airstones.... increase your pumping cycle... and/or "tee" off your pump line to supply your sump with extra oxygen and water flow...

Or move the goldies to a deeper/cooler pond/tank....

Oxygenatio/aeration is your key I think....

+1

They look like rub marks. Any idea if heavy metal would accumulate in the lowest part of a system.

The sump is the biggest pond at 1450 litres (850 when pumping). The other three tanks operate at about 400L each. However, sump is about 50cm water depth during pumping. Temps in the sump are generally about 0.5 to 1 degree warmer than the other ponds.

Now, several things have happened since this morning. Firstly, we dragged a dead goldfish off the top of one of the smaller ponds (the one where I saw the "happy, healthy" fish this morning). There appears to be one dead at the bottom of another pond. So we can stop looking for theories about why different tanks behave differently.

Secondly, we took the sick goldfish to the shop where my wife bought them. Had a look at the other fish there, and they all have the same discolouration of the scales and generally don't look 100% healthy. So we can stop looking for theories based on the fish's appearance.

I'm back to thinking this is straight Ammonia toxicity, brought about by high temperatures and high pH. Have bought some "pH down" from the aquarium shop (doesn't go very far in a 2600-litre system - may need a more cost-effective measure in future). Also bought a 25kg bag of Sunray pool salt and will go and dose the system to 2 ppt after lunch.

Should I add some shell grit to the growbeds to add CaCO3 to the system and boost the hardness?

Oh, and in my travels I found that the "rainwater conditioner" that I bought for my Dad's system a few years ago contains antibacterial agents - no wonder we couldn't ever get the nitrates up...

Nope ... CaCO3... will buffer your pH.... raise your "alkalinity".... not what you need at the moment...

For hardness... use Gysum (Calcium Sulphate) or Epsom Salts (Magnesium Sulphate)....

But I wouldn't worry about your hardness in general.... and I would be messing with too many water quality parameters at the moment... other than those that need direct attention...

Ammonia, pH.... water temp and oxygenation..... can deal with all (short term) with several 25-30% water changes....

And some airstones..... definitely in the sump.....