Backyard Aquaponics
A place to discuss aquaponics

tilapia fish dying almost 40 in the last week...
Here is a quick one minute video to show you our system .. details of water quality are below… http://www.balancedhealthtoday.com/aquaponics.mp4 Finally, have a system up and running , producing vegetables. I am going to attach pictures here.
We have 5 tanks for veggies, only one is really filled due to not having the right balance . Total water in the 5 tanks is around 4500 gallons.
Fish tanks – two 300 gallon Rubbermaid tanks full of about 12 – 1 pound white tilapia and a few nile ( think they are nile – the grey ones ) and the other tank had about 50-70 of varying sizes from about ½ pound to 1/3 pound to 2 to 3 month old fingerlings.
All of a sudden we started getting fish death, previously no problem but we are new to this our system is only about 6-8 months old and we just got veggies really going.
We don’t really have a filter system on it yet. we have a md5 water pump on it. Oxygen levels have always been 5.0 and higher. Ammonia did go to 6.0 and one time before this happened and we changed about 300 gallons of water and corrected it pretty quickly. We are not sure why that happened. Ammonia has been normal every since. 1.0 or less. Nitrates 80ppm , Nitrites were about 3.0. Measuring nitrates and nitrites with strips not sure how accurate. Ph balance is always around 6.0 to 6.5. Water temp is around 74 to 78 . we live in Hawaii ( haiku ) I met you briefly in front of the supermarket when you were taking that meditation class. The fish that are dying at this point are only the smaller fish in the one tank that I said are a ½ pound or under and some are still alive. What happens to them is they start swimming real slow. They will let us touch them. We can grab them with our hand if we want. They are kind of dazed , like they are on a drug or something. Some will swim to the surface but not as if they need oxygen , some don’t. they just stay at the bottom. It is odd. I am afraid it might end up affecting the bigger fish eventually but it has not yet ( the ones in the connected tank ) . This has been occurring slowly. It is not right away. It takes them time to die. Not a quick die off.
One thing I know we need to add is a bio-filter system but it does not make sense as the only thing that was out of wack was ammonia for a short time and I think nitrites are a bit high too. Of course, there are some things we could of missed but any help would be greatly appreciated.
Thank you,
Paul

I'd say your fish died from nitrite poisoning...

How many fish do you have all up?

So you have no filtration at all? No grow beds, just the deep water tanks for your plants.

With no biofilter every single fish is doomed..... doomed i say!!

yes, i guess that is the hard lesson here. Slacking on our biofilter has caused us major problems. That is our project tmrw. Biofilter. I think it is nitrite poisoning as another said. That is why the smaller fish are going first. i have that under control now but need to get the biofilter to keep it that way.

i probably have about 80 or 90 fish total. 12 or so are over a pound and they are in another connecting tank. Those fish are fine at this point in time. Then we had about 65-80 fish in the other tank and we have lost more than 1/2. those were all less than 1/2 a pound and some decent size fingerlings mixed in too.

It's hard to lose so many fish. You should be outside building your biofilter system NOW. It will take some time to get working as it should but you have the advantage that you obviously have some bacteria already in the plant tanks. Maybe divert water directly from those tanks to your GB or filter for a bit to give it the best start?

Good luck - hope you don't lose any more fish.

If you havent already, add some pool salt, between 1 and 2 ppt - 1kg for every 1000L
helps mitigate the nitrites.

will just doing water changes help to reduce the nitrites too? Is sea salt fine to use too? since i only have 600 gallons of water in the fish tanks and the other 4400 gallons is in the raft beds. most of the sytem does not have plants in it yet. only 2 beds out of 5 do. that would be a lot of salt. if i did my math correctly 10kg... could adding that much salt cause other problems?

No adding that much salt wont cause a problem at all... hopefully it will solve you problem... or at least buy you the time necessary to get your bio-filter installed and operating...

what if the problem turns out not to be nitrites? Would it be a problem then?

I lost a couple of fish recently to who-knows-what and salted to 3ppt to help. Fish picked up and started eating and it isn't high enough to cause problems with plants - unless you have something very salt-intolerant you will be fine.

Yes. But if your source water is chorinated town water, take the time to de-chlorinate first it to reduce further stress to your fish

Sea salt is fine, eg swimming pool salt. We can buy it by the 20kg bag here in oz. Make sure it hasn't got any other additives in it.

Your maths seems right to me - 10kg of salt for 2600 gallons (10 000 litres) of water. The salt will also help protect the fish's slime coat. Your plants should be fine with 1ppt salt. Strawberries can be pretty sensitive to it however, but what other choice do you have?

Get that biofilter up ASAP (what were you thinking!?)

If you know a mate with an established pond or aquarium see if you can grab some of the waste out of it to add to your biofilter to help speed up your cycling process.

No.

Some even consistantly salt to 1ppt as a preemptive protective measure

i did a reading just now. My nitrite is at .5..everything else is in a nice range. i am wondering if i should do anything? Would you suggest maybe i isolate the smaller fish and add salt to a separate tank? does salt do more for the fish than neutralize nitrites? It seems like it would as salt is a known drawing agent. Everything has their toxic levels but at the same time there is usually a way to neutralize an internal poison. The problem is this little guys don't weigh to much.