dying fish

[SantaMonica]

Sound exactly like lack of oxygen.

[tjsmk8]

Sound exactly like lack of oxygen.

What do you think the cause of this is? I keep the powerheads in the tank running while cleaning the screen for this very reason (since the return pump is off). I generally have the return off for about 15 mins during cleaning. I turn all flow off daily for about 10 during feeding.

Are hobbyist grade oxygen test kits any good? I'm willing to get one if it's worth it. Is there anything about cleaning the screen that would cause oxygen to drop (other than the return pump being off)?

[SantaMonica]

Just watch the fish and see if they go the surface.

[Rumpy Pumpy]

Very odd.

You could try aerating the water while you clean the screen, perhaps for 10 mins before you start.

[Rumpy Pumpy]

Is there anything about cleaning the screen that would cause oxygen to drop (other than the return pump being off)?

Algae releases oxygen (when lit) so I guess that cleaning off the algae will reduce the oxygen in the tank water somewhat.

No one else, to my knowledge, has reported problems like this though.

I suppose it's possible that in your particular case, the oxygenation level of the water is at a borderline and that removing the algae tips it into inadequacy?

Seems unlikely but stranger things have happened.

[iggy]

Would really need a full tank description before so readers are not grasping at straws.

How much live rock and sand in tank?
How many fish total?

Breeder tanks usually have lots of surface area so your slow must be bad. They may be sick fish that were stressed instead.

[Dallas reefer]

You probably should have plumbed your overflow with a secondary drain, if you supply your ATS with overflow water. On my set-up as you can see, the middle valve is my secondary drain for when I clean it. The first is for my fuge.

And it's all a cheap set up.

[new2scrub]

maybe toxic algae? maybe tiny toxic jelly fish or some other tiny toxic invert is living in you scrubber and being flushed into the display tank during cleanings? Or maybe something is wrong with you system and when you remove you filter(clean) you get a huge spike?

[SantaMonica]

There is no toxic algae in a tank. Algae is toxic when it blocks the sun from reaching all plant life, and when it dies off in huge amounts and takes oxygen with it. Algae on a screen is a tiny amount, and is not dying, and it is not blocking light from reaching corals.

[tjsmk8]

Thanks for all of the ideas. I cleaned the screen again tonight (8 days). I've not seen anything die, but there is definitely some stress in the tank. Malu nem is closed up (does this on occasion so may not be anything), torch coral withdrawn (very rare), neon trumpet closed (first I've ever noticed), etc.

The screen doesn't seem to be growing like I thought it would (based on net progress pics). I do have quite a bit of chaeto growing in the sump below it. Should I slowly trim the macro back? Could it be hindering the screen? I had expected the screen to starve it out, but the chaeto is definitely winning so far (the screen had a month head start).