DOC 9004 Surface Skimming

ktn87

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I own a DOC 9004 skimmer which I bought in 2017. It work great skimming the surface of my frag tank and I recently bought another one which has the air adjustment box connected to the top magnet.

I can't seem to adjust the new one to skim the surface of my tank. There's an oily film which I'm trying to get rid of. But I can't seem to adjust it to do so. I have try raising and lowering it as well as adjusting the air intake. But I can't create the water fall that my old 9004 has.

I installed it just last week, does it need to break in? Or is there something I am missing?
 

rvitko

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This adjustment is all depth dependent. If more of the intake is submerged, more sub surface water is removed. The ideal for maximum surface skimming is to set it fairly shallow, just a bit more than 1/4th of the intake submerged. On a mechanical end, unless the plate the pump is on is installed wrong or the pump is detached, there is no plausible mechanical culprit. The only change was the silencer. I have had many tanks that for various reasons surface film is an issue and things I have noted as causes are flow and feeding as well as dust in the room. I have had a couple flow patterns that basically bisected the tank and wouldn't allow the surface film on one side to move to the skimmer, so flow pattern will play a role. If you feed more oily foods, the surface film is more pronounced and in a dusty environment, it is also worse.
 
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ktn87

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I disassembled the unit and didn't see anything out of place. From what I can tell, the pump is not pumping water fast enough and the chamber where surface water flow into is full all the time.
 

ajm83

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Does the DOC have the little blanking plate like the normal 9004? If that comes out of place (or as in my case was loose in the box) it can cause this issue.

edit to add, it used to be part number 0900.110 as i had to order one years back, but I cant find it on the website any more.

here's a pic of the missing bit (the roughly rectangular open bit at the bottom under the circular hole should be closed off by blanking plate).
wqvp0Xll.jpg
 
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rvitko

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I was just going to say what ajm83 said, this would be the most plausible cause of a loss of pressure. If this plate is missing, the skimmer is sucking in the water inside instead of new water from the intake.
 

ajm83

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I was just going to say what ajm83 said, this would be the most plausible cause of a loss of pressure. If this plate is missing, the skimmer is sucking in the water inside instead of new water from the intake.
Actually it was you who helped me get mine sorted a few years back on Reef Central, thanks! :)
 
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ktn87

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Does the DOC have the little blanking plate like the normal 9004? If that comes out of place (or as in my case was loose in the box) it can cause this issue.

edit to add, it used to be part number 0900.110 as i had to order one years back, but I cant find it on the website any more.

here's a pic of the missing bit (the roughly rectangular open bit at the bottom under the circular hole should be closed off by blanking plate).
wqvp0Xll.jpg

Thanks for that. It was missing and I found it inside the little zip lock bag containing the magnet spacers. After putting it on the pump I'm now able to create the waterfall effect in the intake chamber. I expect the surface film to be gone soon.
 
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