Damn shame... When you figure out what happened (and I bet you will), post a follow up, I'm curious.

You might check your ph, but it takes about 30 days for the nitrifying bacteria in a new tank to get colonized. You're supposed to start with one fish, keep it for a month, and then gradually add more. You might not have to go that slow, but the idea is to start small and let all your bacteria get colonized.

You can also cycle it without fish using plain ammonia (no perfume or surfactant).
Seems unlikely 50 small fish would die overnight in 900L of fresh water due to ammonia or nitrite poisoning, it wouldnt spike that fast. Test kits (ph, ammonia, nitrite and nitrate) are a worthwhile investment for aquaponics.
Did you wash the gravel thoroughly? If the ph is within bounds (ph 6-7), it may be the gravel had some toxic residue on it that poisoned the water.

This post was edited by hex2006 on Tue, Apr 23, 13 at 8:29

First off do you have a fresh water test kit? You should get one if you don't have one.

Second how much are you feeding the fish? You should look up the proper amount for the type of fish you have.

Third did you put fish in the day your setup was complete?
I waited and did the water tests, it took a month to have the system cycle enough to put in the fish. They were very happy when they did go in and were eating in under 5 seconds. There was algae on the side of the fish tank ;)

For the fish to be happy in the system it needs to remove the fish waste. I doubt your fish died overnight do to fish waste. It may be lack of Oxygen or chemicals in the water like cholrine or maybe PH.

Ok all, thanks heaps for your help. Maybe I was premature putting in all them fish just as finished the set up. But one thing is for sure, it wasn't ammonia or lack of oxygen or pH. I emptied the tank and cleaned it out a few says later. I then filled it with fresh oxygen rich water and add a water conditioner . I didn't cycle the water so it didn't go anywhere near the growing media. I bought 2 gold fish and popped them in. Within half hour they were at the bottom just hanging and looking very sad. I quickly removed them and put them in our small indoor aquarium to try save them. They were dead within the hour.
Then thinking about it the indoor aquarium uses the same water with the conditioner and houses 2 thriving goldfish.
So in the Aquaponics tank there is a fitting that goes through the wall to the pump. I accidentally tore the pond liner too far when fitting it so painted some bitumen paste over it to seal it. The container says nothing about being toxic to marine life but it Must be the killer. It's the only thing I can think of.
Going to remove the fitting and reline the pond and fit a new one and see how that works. But will first cycle for a month. Do I put plants in the medium while cycling? Couple of lettuce plants or something?
Cheers

Dan

Fishless cycling would be quicker as you can optimise it for the bacteria (no fish to kill). Higher ammonia concentrations (upto 5ppm), higher ph and temperature.
It would be a good idea (if you can) to innoculate the AP system using some mature filter medium from your established aquarium.
I wouldnt put any plants into the system until its completely cycled so you can track the nitrate level. Nitrobacter reproduce much slower than nitrosoma so it`ll be a while before you get any significant nitrate production.

I also anticipated this might happen to me in a certain degree.

Some measures I took to avoid this problem having is:

Medium:
My rocks are black lava rock and came in individual bags from Home Depot (the spongy porosity of lava rock deposits lots of nitrates for roots to gravitate to). They are specifically made for landscaping and growing mediums. It is more expensive but I had a friend who picked up his rocks from one of those places where you drive in a truck, weight it (so when you weight out they know how much you picked up), and back it up into a stall with a mountain of gravel you use a motor shovel lift to fill up with. He found a lot of tainted stuff when he concluded he needed to perform an all around chemical test on the water he contaminated with this gravel. It ended up having a lot of other stuff we couldn't agriculturally test for.

Introducing living organisms into new habitations:
I am told that whenever you transfer primitive aquatic life into a new environment they should be stabilized from any sort of shock. Shock meaning so scared and frightened by sudden change that primitive creatures will not facilitate their niche in a routine that sustains them for the duration of stabilizing (or other organisms piggy backing).

1: I introduced 30 fish at first into a 200 gallon system, and about 10 gallons live (pipe, sump, and whatever is left in the bed below your bell siphon shut off level). The rule of thumb is about 1lb fish per 3-5 gallon, or roughly something like that. My fish tank holds about 60 gallons (growing bed is 1' by 3' by 7 1/2' with 9" cycle, and 3" water table. The fish have a metabolizing rate and this is what governs the colonizing speed of the bacteria that Hex2006 is referring to. After a week I introduced 60 more goldfish. I lost 3 fish in the process by natural selection (hypothesis based on the 3 were some of the very smallest of the group and looked underfed).

>>>Do I put plants in the medium while cycling? >>>Couple of lettuce plants or something?I let my system cycle for 3 days (one cycle to fill is 12 min, and to evacuate the grow bed is 8 min). This roughly states that the speed in which I can expel the water from my grow beds will be about 1/2 as fast to fill it, after calculating out of boredom from sitting for hours calibrating different down pipes and bell siphon (i guess algebra paid off after all...).
I did in fact have "some" plants in it when I did. So the methodology will seem backwards here, but I ask, which came first, the chicken or the egg? Hence I added what I had left over of "fish chum" but it was actually product vigorgro that was basically emulsion of fish from a blender, yum (I stopped using it because it stunk up my indoor HP system). This fed the plants I had in the system for three days and started the cycle. I later balance the pH before adding powder soluble HP system 'nutes'. The plants I had in first were lots of snap string beans, beets, and lots of collard greens. For time of year I was building this, I used plants familiar to me that had high metabolite and are easy to propagate in lava rock.

>>>First off do you have a fresh water test kit? You should get one if you don't have one.should = MUST

>>>Second how much are you feeding the fish? You should look up the proper amount for the type of fish you have.Fish in new habitats should be allowed to almost starve til the end of the 2nd week (or later if colder), until you start seeing a rise in pH above 6. Fish must actually create their OWN environment assimilated from their own feces to feed the bacterial colonies that will reside in the symbiotic niche between micro organisms, the fish, and your plants. Most your plants have much of the same chemical compounds, but fish being a carbon based organism will obviously have a more complex compound of chemicals, especially what you feed it.
A. Starve the fish for more then a week
B. Start feeding the fish very little once the water start to look clearer (the fish breath through their gills, and whatever small particle they filter, they eat; even microscopic beyond eye threshold.
C. Always under feed the fish; if after feeding there is still food floating or at the bottom, skip a feeding (a day).
D. Keep it organic, no store bought stuff for your fish that comes in a box. The fish poo > nitrites > nitrates > plants > then into your mouth... Trash in trash out. Keep it fresh. I eat a lot of rice, and always have left over rice. Cereal that goes bad (avoid honey and fruits: corn flake are ideal, bran anything). Crumple it up for the fish to eat bite sized; stone and mortar.

I have built a few AP systems for friends, and even built a gazebo deck around a fish tank at a buddies. This is proven advice.

I have a question for you if you still check this thread:

Where is your sump?

Your garden bed seems to drain right into your fish habitation. I've been told not to do this. There should be a intermediate percolation that dilutes both incoming solutions between the two. Not that it's toxic, but it does cause fish to feel shocked and imbalance within their habitation. Ammonia, oxygen, and other impurities, like living in LA then suddenly at the base camp of the Himalayan as a human analogy.

I also just personally think fish would not like listening to the hum of a hydro pump (whatever size it may be) 24-7 LOL!

I will post follow up links to pictures:

Here is a link that might be useful: {{gwi:1004157}}

My Aquaponic system:
{{gwi:1004159}}
{{gwi:1004161}}
{{gwi:1004163}}

My Hydroponic system
{{gwi:1004165}}
{{gwi:1004167}}
{{gwi:1004169}}
{{gwi:1004171}}
{{gwi:1004173}}
{{gwi:1004176}}
{{gwi:1004178}}
{{gwi:1004180}}

Some plants coming out of the hydro system going into the aquaponics: in transit. I used Wine bottle boxes that have the inlaid partitions.
{{gwi:1004182}}

Thanks for the advice moon.
Iv actually sorted the problem out and am fully cycled with 50 healthy goldfish been alive for 4 weeks now. The problem was the bore water. Luckily we also have a water tank that collects rain water so the bore water goes nowhere near my fish tank. Great idea with corn flakes etc for a feed alternative. I bought brine flakes to feed them. Maybe should have researched feed before I bought a kilo of the stuff!
Also from my research the sump tank is used to keep the fish tank level not too low and stress the fish but is not needed in this case as each bed fills up in sequence through an indexing valve, the water level only falls about 100mm maximum. Do correct me if I'm wrong though. Also it's not a submersible pump, the pump is in the ground outside the tank, fish can't even hear it.
Dan

Sorry that was supposed to read.......
Thanks for the advice mdon (damn predictive text!)

I'm dealing with a relatively new aquaponics system and that I constructed about a month ago, and I put goldfish in it immediately. I bought 10 small goldfish from a pet store (feeders) and none died for more than a week, and then since then they started dying one or two each night. I bought an additional 100 and am currently down to 20. I am using red lava rock, and my plants a thriving. I have been very concerned about graduating to tilapia and catfish (my plan) but until the goldfish can live uninterrupted I will not graduate.

I had conditioned the water originally, and what I have noticed is that the water is clear but not colorless. It is in fact quite yellow. I have been wondering if the problem is that the plastic container I am using, 27 gallon black totes from Home Depot and Lowe's, is leaching a toxic chemical into the water.

I am experimenting now with a side 27 gal tote that I put fresh water into yesterday, let sit out and allow chlorine to evaporate for 48 hrs, that I am not cycling with my system. I have moved my fish to it and they appear to be more lively. This will tell me if the tote is causing the issue.

I'm hypothesising that the water running through my beds is somehow not healthy for my fish. I will also buy a water tester tomorrow.

Thank you guys for your posts, I learned from them. If you have any ideas or additional support I am all ears.

I will post result in a few days.