Fish keep on dying? Is my closed loop the culprit?

[tgunn]

Hrm, I seem to have a might of a mystery on my hands here. In the past month I have now lost two larger fish from my tank.
Earlier in July I lost my powder blue tank; I looked into the tank and it was all beaten up and stuck to the closed loop intake.
Just today my wife called and said that the new Kole (who just went in end of June) was dead ands tuck to the closed loop intake.

I had originally thought the powder blue died because of the fact the new Kole was pretty aggressive.

Here are my intake screens:



I have a 1 1/2" bulkhead that acts as the tank drain. I used a Wye to split that to the two intake screens you see. Each screen is the same diameter as 2" PVC and about 5-6" tall.

The closed loop pump is a Sequence 1000 SEQ 22, which pulls around 4500-5000 GPH, and distributes it via 8 x 1" outlets in the tank..

In the past I had a single screen made with a finer screening material, and I had a Sailfin end up dead on that.

I'm really at a loss here.

My parameters all checked out last time I looked.
Salinity: 1.026
Temp: 78.5F (stable too)
Nitrates: 0
Free and total chlorine (tested with Hach kit): 0

I had a problem with overdosing ozone in the past when I went to my new skimmer; I was reading high OPOs, but am not reading anything now. I'm running my ozone unit on the lowest possible setting, and it's controlled by an ORP controller such that it only really raises the tank ORP by perhaps 10 meV or less.

Opinions and advice are welcome.

Could my closed loop intake be the culprit? Any opinions on my screens and if it's just too much flow for the intake screens? I always assumed that the fish couldn't really get caught on these, but it seems the dead ones are always turning up on the screens.

Or... Could there be an underlying problem with the chemistry I'm not seeing that is causing this? Could the ozone still be the problem?

Thanks in advance for the help!
Tyler

[mhurley]

Very unlikely that the closed loop is the problem. More likely is that the fish died, floated around and got sucked into the intakes.

Ozone can definitely kill livestock but if your ORP is back in line, it should be fine. What is your current ORP?

I'm banking on sick/injured fish that just died or an underlying chemistry problem.

[tgunn]

Originally posted by mhurley
Very unlikely that the closed loop is the problem. More likely is that the fish died, floated around and got sucked into the intakes.

Ozone can definitely kill livestock but if your ORP is back in line, it should be fine. What is your current ORP?

I'm banking on sick/injured fish that just died or an underlying chemistry problem.

My inclination is that it shouldn't be the closed loop, but I dunno, this is the third one. I read another thread somewhere that sleeping fish can sometimes drift and get stuck on CL intakes? could be the case here??? I dunno.

I'm not sure what my exact current ORP is right now. My ORP probe has drifted upwards from the actual(time for a good cleaning). Without running ozone at all for a number of days it registers around 405 mEv. With the ozone it reads around 415-419mEv. I basically let it sit for a long while, and then just turned up the controller a tiny bit and left it there. Clearly not running accurate right now.

No readings of chlorine in the tank, so not likely OPOs.

I dunno, the Kole seemed quite healthy and happy, as did the Powder Blue up until it just packed it in...

I'm really drawing a blank for what else the problem could be here.

Tyler

[mhurley]

You've got a 5000 GPH closed loop on a 140 gallon tank?

Those fish must be surfing in there for sure. ;D

Not sure, but Powder Blue's don't have the best record of getting established overall. But even a sleeping fish like a tang should be able to get away from those intakes. It's one thing to have they sucked against a intake hole...but you've got strainers that distributes the flow there is not that much draw at a given point to where a big strong fish can't get away.

[tgunn]

Originally posted by mhurley
You've got a 5000 GPH closed loop on a 140 gallon tank?

Those fish must be surfing in there for sure. ;D

Not sure, but Powder Blue's don't have the best record of getting established overall. But even a sleeping fish like a tang should be able to get away from those intakes. It's one thing to have they sucked against a intake hole...but you've got strainers that distributes the flow there is not that much draw at a given point to where a big strong fish can't get away.

Yup, 5000GPH closed loop and probably around 1000GPH through the sump. Too much you think?

I still wonder if it's just too much flow through those screens and in the tank overall. It's only the larger fish that have seemed to have problems. Perhaps I'll have to stick my hand in there and see how much suction I feel on my hand cupped around the side of the intake screen. Perhaps it's just too much for the larger fish? I really duno.

My fish load is extremely low; I have 1 clown, 1 chromis, 1 yellow tang, and 2 cardinals. So I'm reasonably sure pollution isn't a factor.

Thanks for the help,
Tyler