Pond Boss Forums GENERAL QUESTIONS Help My tilapia are biting the dust

Hello everyone, I am in a rather frantic panic, for my beloved tilapia are dying. The only symptoms I see from them is lethargy, loss of appetite, and physically their underbellies are sunk inward. I did an autopsy and when I cut into them, a green fluid came out. Each day about 5 or so fish will get sick and die later on in the night. I don't know what to do at this point. Not sure if anyone else has had a problem like this, with tilapia or any other fish. Some feedback would be appreciated tremendously. Thanks. -Elliot

Need to have some questions answered first:

Are there other species in the pond?

If so, are the tilapia the only species dying?

How large is the pond in surface area?

Do you feed the tilapia?

Any noticeable changes in water color or appearance?

Have you recently had a thunderstorm with a fairly significant amount of rain?

An increase or decrease in aquatic vegetation?

Is the fish population high?

Do you mix the water column with a diffuser?

I've cleaned healthy Tilapia for the table and had the same green fluid.

Sunken stomachs? What is in the pond for them to eat? How big is the pond, and how many Tilapia?

Try these for info

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92438#Post92438

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92486#Post92486

They're in a plastic pond, about 700 gallons. 500 or so tilapia. But no, nothing out of the ordinary has happened with their environment. I may have been overfeedin. Ammonia and nitrite was about .25ppm.. The skin turned darkly pigmented just on ones head yesterday and seemed to have no energy.. I've been feeding them only once per day since it began to happen. Other then purina grower 600 they have nothing else, some duck weed too when I put it in.

Tilapia is the only breed in there, and I have air stones.. I don't believe oxygen is the problem

What are you using for filtration, how many pounds of fish do you have per gallon and how many pounds of food are/were you feeding daly?

700 gallons and 500 fish? yikes!
how much air do you have going in?
how big are these fish? and yeah, you need gobs of filtration..
what kind of turnover in the tank? (how often does the volume of tankwater turnover?
with that many fish, i'd have pure o2 injection..

i have a 700 gallon tank (or so) and would be pushing it to capacity with 200 adult fish..

oh, and do you have some kind of backup power?

Filtration is a Cetus, with 100 micron screen, then the water goes through a 20" 50micron canister filter. These get washed on a daily basis. I fed them twice sometimes three times per day. Hard to say how many pounds of food I'd go through. I do have a question though, on the sides of the pond the plastic has a brown coating on it, algae like. Is this beneficial bacteria, or do I want to scrub it off?

A pool pump cycles the water, and runs continuously, Im not sure of a formula to use to find the ideal turnover. The fish are right around 5oz, four inches on length I'd say.. Back up power, oh god yeah.

What is the capacity of your biological filter (i.e. what's the filter rated for)?

What species of tilapia do you have in the tank?

Both Ammonia and Nitrite readings were the same at .25ppm?

So you're estimating that there's about 150# of Tilapia in there now?

How large do you want to grow the Tilapia before removing them from the tank?

I'm only seeing mechanical filtration here. No biological except for the tank surfaces. This in itself would explain your losses and they will only get worse.

I'm guessing ammona is quite high for tilapa to die. You're lucky you don't have bluegill or yellow perch in the tank. They would all be dead.

What is your Ph? If your Ph is high it will compound your unionized ammonia which is the component of ammonia that is the toxic one.

Sorry for being blunt but just telling you like it is. I have three hundred tilapia and bluegill up to 6 inches in a 600 gallon tank with no issues. However I have 4 cubic feet of plastic media for biofiltration along with a mechanical filter. The water also runs through a 48 cubic foot raft tank for additional biofiltration and I keep the ph slightly acidic.

Pool pumps and filters are not a good option for raising fish.

I'm with Keith on this one. Not sure how you been getting by with it but you are now seeing what's gonna happen. You have waaaaaaaay to many fish in there at 4 inches.

Hate to say it but a good rule of thumb is to use the 1 inch per gallon rule. Anotherwards if you have a 10 gallon tank you can have 10 inches of fish. No it's not a perfect system but it does help keep you close.

So in your case 700 gallons, take that number and divide by 4 cause you said the fish are 4 inches, and you end up with 175. So there you go. Hate to say it but Keith is right! Well I don't hate to say it cause I don't even know Keith but anyway he is right on. You should not have no more than 200 fish in that tank!

RC

even a broken military clock is right once a day! lol

anyways, as cecil and other's have mentioned, you need biological filtration, basically, surface are for bacteria to grow on.. i'm using three "half" ibc totes full of gravel for biologic filtration

you could probably put a couple of 55 gallon blue barrels in series and fill with something like matala matting (i use floor buffer pads) and bird netting...

Rainman may also be able to provide good insight. I think the others are correct especially if you do not have a large biological filter in operation for the grow tank. ""The only symptoms I see from them is lethargy, loss of appetite, and physically their underbellies are sunk inward. I did an autopsy and when I cut into them, a green fluid came out."" These symptoms in crowded conditions sounds like ammonia poisoning. The green fluid is bile fluid from the gall bladder; you cut it during dissection.

Actually guys I don't believe it's the numbers one should consider, it's pounds of fish per gallons or cubic feet, and even more specifically how much feed you are throwing into the system. Just recently I had about 1000 yellow perch in a 170 gallon tank before I graded the largest ones out. No problems whatsoever since they were only 2 to 3 inches and I had plenty of biofiltration and aeration. And pound wise the total was quite small.

I've had up to 1/2 pounds per gallon of 7 to 9 inch yellow perch in that same tank with 4 cubic feet of media in a moving bed filter and aeration with no issues. However I was doing a 10 percent water change every day when I got to that point, and cleaning the clarifier at the same time. The tank is circular tank with a center drain with centripetal flow so the settleable solids went to the center drain and were flushed out twice a day via an external standpipe. The suspended solids were sucked into a siphon and trapped in the clarifier. Simple but works great. It would have been even better if the solids were removed right away on a continuous basis such as a rotary drum filter but at this point that is above my pay grade.

Typically if you're not a hard core commercial outfit most literature says not go above 1/4 to 1/2 pound per gallon, and if you do go above 1/2 to 3/4 pound per gallon you will need to use pure oxygen. The big commercial systems that are pushing 2 lbs. per gallon of tilapia have all kinds of back up, and if something does fail they can loose their fish in a matter of minutes. And of course their tanks are self cleaning with solids leaving ASAP.

Thanks for the input. I did however forget about my biofiltration above. I have a 250 gallon tank half full of bio balls, and the rest is filled with plastic pieces which have generous amounts of surface area. Now that I think about it, the temperature in the tanks has gone up since I've turned the heaters back on. Which would limit oxygen levels to some extent. As for the pool pump, it gravity feeds over the 100 micron screen which catches solids, then goes into the pump, through the house filter and into the bio. I've had the water going into the pump before the screen in the past, and all that does is break apart solids and makes for terrible filter there on.

I think I need more DO. Ammonia really I'm not sure is the case, .25. Come on. Water smells and looks good. Ph is basic. I cut down on the feeding, went from 40% protein down to 26%, and to once a day. Just for safety sake that it is an ammonia problem. Do all fish have that green liquid in their gall bladder??

Gall bladders are green. Even yours and mine. LOL

Well if it's not ammonia (assuming your reading is accurate) than oxygen is probably the issue. What do you do to aerate the tank?

First limiting factor is oxygen followed by ammonia. 99 percent of all fish kills can be attributed to low oxygen.

Green, hmm I seee. Ha! I have like a 6"x6" air pump and have a splitter off that with 7 air stones..which may not be sufficient. I'd like to get something a little larger. You can never have to much oxygen

Just a thought. Since tilapia as I understand it are primarily a plant eating fish (algae) perhaps the 46% protein food was just too much for their diet.

Actually RC51 the one inch per gallon rule is pretty much for aquariums where producing as many fish as possible is not the goal. Keeping the water gin clear and the fish just floating around for viewing is.

I.e. many ras systems grown maintain at least 0.5 pounds per gallon. If you had 0.5 pounds of fish per gallon in a 20 gallon aquarium you'd have 10 pounds of fish in there! LOL Even at 0.25 lbs. per gallon that would be excessive for an aquarium.

Some intense systems with supplemental oxygen, UV, and ozone grow up to 2 lbs. per gallon of tilpia. That would be 40 lbs. of fish in a 20 gallon aquarium!

I suppose your right Cecil but pushing things to the limit and over crowding can get you exactly where CCF is right now. And can be very hard to get out of it once said fish start to die.... Hope you can break the chain CCF... and figure out what's going on.

RC

Thank you, yeah I think I'm going to try and disturb the water that flows back to the tank so I get a little more oxygen exchange. Cecil, I forgot all about supplemental oxygen. Just get a tank filled at 2000psi, then regulate it to 5psi or however going into the fish water. That should last a decent amount if time. Is there any way to find out what DO level is in a pond?