Backyard Aquaponics
A place to discuss aquaponics

20 Sep 08 1130am: purchased 75 4-6" catfish.
20 Sep 08 1230pm: Placed said fish in 150 gal tank that has been sitting for 1 week with chlorinated water. No treatment and I didn't check the water. Fed approx. 1 cup floating fish food.
20 Sep 08 0900pm: checked fish.....swimming on surface and eating.
21 Sep 08 0700am: 75 dead 4-6" catfish.

One item....timer on pump not working.....no circulation of water. Would the fish deplete the oxygen that quickly.

in a word. yes.

my 30 odd trout can deplete the O2 to the point where they swim at the surface (thats your cue to man battle stations) happens in about 5 hours when the pumps stop.

Yep... no pump, no oxygenation...

Fish stressed through transport... high metabolism... elevated oxygen consumption...

Fish fed... elevated oxygen consumption... (raised metabolism) to burn food...

Elevated oxygen consumption.... no oxygenation... elevated, rapid, fatal oxygen depletion...

Also would have had elevated levels of ammonia waste excretion, due to stress, metabolism, feed....

And 75 x 6-8" fish in 150 gal (600ltr) was probably pushing it to the limit of what your capacity could handle anyway.... assuming you were cycled beforehand... and had 2:1 bio-filtration....

(works out at about 6+kg/100ltr).... I would have halved the amount of fish ... unless you had a fully cycled 2:1 growbed filtraion capacity... and the system was 12 months old...

Especially with fish that size....

Water temperature would also have played a part... both in terms of DO and ammonia toxicity...

Rule #1 .... don't over stock fish in a new system....
Rule #2 .... don't feed your fish for at least the first day.... they're pooping and excreting anyway...
Rule #3 .... monitor water quality at least every two hours or more frequently ...
Rule #4 .... be preared to do water changes (up to 50% at a time)...
Rule #5 .... leave your pump running 24/7 for the first day or two....
Rule #6 .... have supplementary aeration available/running....
Rule #7 .... re-read the rules prior to getting any fish.....

By the way.... I would have thought that catfish would have preferred a sinking pellet ...

Not intended to beat you up... you're probably do enough of that anyway....

I've currently got most my channel catfish in a 300 gallon tank. Granted most of mine were larger when I got them average probably 8-10 inches for mine. I only got 47 catfish at first though and definitely didn't feed the first day.

Anyway, catfish will happily eat floating food. It is handy to stick with floating food since sinking food is harder to clean out if they don't eat it.

Catfish are actually rather sensitive to reduced circulation and reduced O2 in the water. I notice that if the circulation from the pump is reduced due to clogging in the trap basket, the catfish will usually not eat all their food. I've also found that the air stone is often not enough to keep the catfish happy and though they might survive a day or so in my system without the water pump while the air pump is working, I'd better hope that the feed isn't still going in.

The tilapia seem more comfortable with reduced O2 but will stop eating first with polluted water.

How bout an update in your system thread so we can see if there are any measure you need to take before getting more fish. Looks like the last post on your thread didn't even have the plumbing finished.

Is your system already cycled or did you put that large number of fish into a system with no established bio filtration and then feed them?

Checked his thread TCL... 10 x half barrel growbeds... assume 60% media volume...

That's 10 x 100ltr x 60% => about 600ltr of filtration capacity.... a 1:1 ratio....

That was posted end of June....about two months ago... so should be cycled...

Just too many fish, too big, too soon, in a system that wasn't pumping.... plus feeding...

Sounds like the basis of a good little system though.... and what are the chances of a timer/pump failure, just when you get your fish...... ???

Proabably about 100%... according to Murphy....

I just wasn't sure since comment was about a tank filled with previously chlorinated water for a week, it made me think that perhaps the system has not been cycled to build up a bacteria colony.

It does sound like that system that can be successful.

Take heart, everyone has to kill some fish. We just hope that the next ones you kill, will be as you get ready to eat them.

Thanks for all the input. My new timer should arrive in a day or two. Going to hook it up and let it run for a while. Didn't understand that the bacteria would develope without the fiswh. Oh well....lessons learned.

To do fishless cycling, you just need an ammonia source. There are threads about fishless cycling that should be pretty easy to find with a search. A little pure ammonia (no detergent or other additives) if you can find it will work, other methods include urine, urea, or some fish food.
Hopefully you have your test kit and can monitor your cycling. Basically, bring your ammonia level up to 1. Let the system work on it till you notice the ammonia level dropping and the nitrite starting to come up. You can probably add a little more of the source every once in a while. Once the system can take a ammonia reading of 1 and 24 hours later have an ammonia reading of 0 as well as nitrite reading of 0 then you should be cycled.

You can do it with fish but it is so much more stress on you and the fish.

FYI My catfish don't usually swim around at the surface. If they are, it means need more O2. They usually only come up to the surface to grab food then dive back down.