Backyard Aquaponics
A place to discuss aquaponics

I think the galvanized issue is still under debate with no real answer either way.
I have a galvanized tank and I lined it with clear polyethylene sheeting, because I just wanted to be on the safe side. Some how it got a few holes in it that i can't find, now there is water between my liner and the tank wall. So I don't know if the liner is doing any good now.
One bad thing is , the liner has caused quite a few fish loses because the ends are pleated and have trapped some small fish in the folds when the pump was cycling and the water level dropped.

I wish I could find out for sure about the effects of galvanized because I really want to tear my liner out.

-Stevo

I have no idea about long term issues with Gal - ie once it has aged a bit. What I do know though is that when using gal wire for aviaries, it is recommended that the wire is washed down with vinegar or something first so that it does not harm the birds. Logic tells me that if fresh gal can harm birds it may also harm fish. Of course the gal for tanks is probably different in terms of application and stuff than that for weldmesh.

Check with the people who made and see if they used aquaplating - thinking on this, didn't forest have fish deaths with her new tank.....looks like I should to give mine a wash before commissioning it as a safety measure

Forest's fish were alive for ages. DIfferent problem I would think. Her's and yours are aquaplated heh.

Yep - that's all Foley's use...be interesting to find out what caused forest's fish deaths.

Had the fish tank "weathering" for a couple of weeks so hopefully that will clear any nasties that may have been there

Smart man Les

Okay... An update.

Dad's approach to aquaponics is "set and forget", and as a result he has lost close to 100% of his fish so far. His Australian Bass have all disappeared but he has 9 enormous goldfish - they seem very fat and very happy. Probably ate all of the Bass. He's not buying any more fish for a while having lost now about $500 on fish deaths.

Plants. His spinach look like bonsai. NOTHING like the superb growth expected from aquaponics. These are plants that have had many months in the system and they still have leaves only about 5-10cm long, very thick and leathery. The stems are thick and woody - almost like "trunks" really. Parsley has yellow leaves. Extremely disappointing plant growth all round, compared with what everyone else seems to obtain through aquaponics. Lots of yellow, almost white, leaves and everything is becoming incredibly leathery. Thicker spinach leaves than you could imagine - they're like big gum leaves!

Given that Dad's main goal is to have fresh, lush vegetables throughout his desert summer (he's in semi-arid SA) this is bitterly disappointing so far. However, despite all this, he still can't find the time to test his water, so whenever I'm there I try to do a test for him. The most recent one was on the weekend.

pH ~ 7.4-7.6 (bottom end of the high pH scale)
NH3 ~ 0.025 - 0.1 ppm
NO2 ~ 1 ppm or less
NO3 ~ 100 ppm (!!!)

So it seems not to be ammonia or nitrite toxicity, but perhaps nitrate toxicity that killed his fish? Interesting that there is such high nitrate but such stunted plant growth. My guess is therefore that some deficiency is preventing the plants from taking up the nitrate. We put some organic "trace mineral" liquid fertiliser in, along some chelated iron powder, and I suggested he continue putting a teaspoon of the iron in once a week for a month or two.

Cheers,
James.

Hi James,

It might be useful if you could dredge your memory banks and go through the systems setup process for us with dates and stuff.

That would give us some idea of the maturity of the system and might help problem solve the reasons for the fish losses.

The time spent for the growbed to flood and drain would be useful, the results of any previous water tests and their dates. There are some pretty smart cookies on this site (allegedly) and they should be able to help you get through this rough patch.

don't give up yet

Thanks trentski. I'll be dredging the memory banks and approximating here...

Summary:
System 1 yr old
Fishtank = Galv tank 1.5m dia 1m high ~ 1500L
Growbed = Galv tank 1.5m dia 0.3m high
The pump can fill the growbed within about 2-3 minutes, and with the current holes it takes about 20-30 minutes to drain.
Ammonia has never been dangerously high (always < 0.1 ppm)
pH has always been within 7-7.6
NO2 has generally been low (< 1 ppm)
NO3 is only now getting up there at ~100ppm
Plants have NEVER grown well and right now in prime NO3 conditions are totally stunted


The setup is pretty much exactly as per the manual. Unfortunately we spent our time researching the construction and (having no experience in fish-keeping) we didn't ever think to study the nitrogent cycle. We were (and still are) naiive.

The system was installed at about this time last year and populated with 100 silver perch fingerlings straight away. That was followed by a period of extreme cold (most mornings air temp ~0 deg C for a fortnight, max temps < 15 deg C), during which I think 97 fish (i.e. 97%) died. At that point, a large aquarium heater was installed on a timer and we started to study the nitrogen cycle in some detail! 10 cheap goldfish were introduced to monitor the system before ordering another large batch.

Silver perch and catfish were bought in a few half-dozen batches from pet stores (expensive). All catfish died within a few days. We identified a major over-feeding issue that was resulting in a toxic sludge accumulating at the bottom of the tank. After cleaning the tank, Dad repositioned the pump so that any uneaten food or solid wastes were sucked up and filtered out by the growbed. We suspect the catfish, being bottom feeders, were being killed when they stuck their heads in this horrible pile of old, uneaten food.

Meanwhile, the goldfish remained healthy and after another month or two, 5 or 6 silver perch also remained and were growing very well. I think it was then, after a couple of months of zero losses, that we decided it was working well enough to try another batch of fingerlings. 100 Australian Bass were ordered and 98% had survived after the first couple of days - a new personal best for Dad!

Then in summer there was a series of 40-45 degree days, and unfortunately Dad went completely the wrong way in an attempt to keep the water cool - i.e. he stopped cycling the water through the growbed in the heat of the day! This led (I believe) to heat-induced nitrite toxicity (1-2 ppm NO2 from memory - toxic in warm water). Also, without the returning water there was no aeration, so nitrite combined with low DO knocked out three or four of the large perch. During that heatwave the tank also became dangerously low on water and the pump cut out altogether for a day or two before Dad discovered it. Surprisingly Bass fared well through the heat, and the goldfish remained very healthy.

The temperature problem was rectified by establishing a schedule of "flood 15, drain 15" running 24 hours a day and a large aerator was installed with backup battery.

The system went well for the first few months of this year, but then the Bass started dying at a rate of approximately 1 per day. There were usually signs of being partially eaten, but that was maybe occurring post-mortem. The remaining silver perch died at some point this year, as did one goldfish. As of a couple of weeks ago, there no more Bass have been visible. The remaining 9 goldfish still look exceptionally healthy.

Suspicions:
I suspect the fact that the plants are so stunted is related to the fact that the fish are dying - both suggest there is something very wrong with the ecosystem.

I don't think the growbed is fully emptying every "drain" cycle - there seems to be a constant flow of water in between pumping events. This may be reducing the effectiveness of the biofilter and/or inhibiting plant growth (depending on just how empty it actually gets).

Owing to (a) the drought, (b) the low annual rainfall (300mm is a good year), and (c) the fact that Dad has ONLY rainwater for his entire house/property, we have not ever pumped out the water and re-filled with new fresh water. If there is some chemical contaminant in there, it will have been cycling through the system continuously. However, I don't think this explains the very slow but steady die-off of the Bass.

Sorry for the long post but it gives a potted history of the system.

Jimmy, I know it is a pain in the rear, but you may have to drain that tank. Some fish are more susceptible to toxins than others. For example, the goldfish are near bullet proof compared to silvers and I suppose, bass.

I am surprised that you have 100 ppm nitrates given only 7 goldfish in 1500 litres. I suspect your test results are incorrect.

Your Dad needs to really monitor the system closely. I feel that something has upset your water and because you haven't changed it out, would still be in the system. This sort of low plant growth would not be due to ntrate toxicity, nor would high nitrates at this level cause fish deaths on its own. Regulaly run nitrate levels of much higher than that in aquaculture are not unheard of. Growth rates may slow and eventually death may occur, but not at that level if all other parameters are acceptable.
I think the fish have been weakened by toxins and a mixture of water temp falls and rises. Are you in an area where people spray crops and is it possible that uyour rainwater has chemical residue in it? Finding the cause of fish deaths is really hard.

Hi Monya,

Thanks for the advice. I am constantly harassing Dad to take more regular measurements and he is constantly telling me "I know, I know".

I have recently suggested at the very least he does the swizzle-stick test for NO2 and NO3, because it is dead easy and takes about 1 minute - plus, the levels of ammonia & pH have never been dangerous. Hopefully he can manage this. He has decided that he won't re-stock with any more fish now until he proves to himself that he has the discipline to check the water regularly, which I think is a good idea.

He is in an area where people use chemical sprays, but these are generally not aerial sprays, and people are pretty good about not spraying in windy weather. I wonder if there could have been something nasty on the gravel right from the outset - it was just scoria and marble, bought from a garden/landscape supplier. Mind you, we washed it thoroughly before we put it in the growbed. And the plants haven't died, they've just gone bonsai and all have thick, leathery leaves. With plenty of spare nitrate, we should be seeing those plants grow like crazy - so there must be something else inhibiting the growth.

I think once he's had some more rain, I'll suggest we do a total water change, and flush the growbed several times.

with regard to plant growth I would also check the water level. I gound that one of my grow beds had substantially lower growth than another when the flood hieght was too high. make sure the water does not come up above 1inch (25mm) from the surface of the gravel. try planing some seeds direct into the gravel. I often cut the top off a plastic drink bottle then drill 1 6mm hole in the side and place on top of where I planted the seed, this acts as a mini greenhouse and can help the early stages of growth.

The water level is definitely flooding too high as there is algae visible at the pipe outlets. As I said before, it is also not draining fully before the next flood cycle.

Oh well, it looks like I'll have to head out there and help him fiddle with his flood & drain.

Hey Jimmy, you really sound as tho ur across the possible whys and wherefors.
Thick leaves are in plants trying not to lose water. Even tho ur plants are flooded and drained regularly, it sounds like they are actually having trouble taking up the water, hence thick leaves to prevent moisture loss. It doesn't sound like pH related nutrient lockout and ur flood/drain could be tweaked but doesn't sound like a system killer.

Quite often gravel is treated with petro chemicals for road surfacing and no amount of washing will clear this. The stuff is IN the gravel.
I think u need to dump the gravel and use hydroton. It is expensive but inert. You will also need to dump that water. Cherish those goldies, they will survive a nuclear winter and re-cycle the new system for you.

Oh ! Is this a possible cause for not being able to take up water:
High dissolved salts/substances/whatever: Plants take up water by osmosis right, so when the concentration of dissolved stuff in the water gets too high (especially as jimmy mentioned they never changed any part of the water the whole time) by feeding, etc, the roots may not be able to suck up the water much by osmosis since it's concentrated outside the roots in the water.

So should jimmy test this if he happens to be able to borrow a conductivity meter or TDS('total dissolved solids') meter?