DNW-200 performance

[boca rat]

Have a recently acquired nearly new DNW-200 and have it hooked to a 150g mixed reef tank, replacing a OCTX160 which worked pretty well for the most part producing a lot of gunk.

Disappointing results so far, even after 2 weeks running on a live rock tank (and many weeks prior to me owning it doing the same thing), and 2 weeks now hooked up to my 150g.

Being fed by half of the return flow from the tank driven by an Eheim 1262 through mostly 3/4" line. I have valves on this return and have most of the flow going into the skimmer.

I have very little skimmate produced.

Where is the ideal water level in the skimmer neck? See attached foto, basically I have it just above the gray screw ring that holds the cup in place.

If I go any higher it basically just skims water. Any lower and I just get gunk in the neck.

Suggestions? What am I doing wrong?

BTW pump is OTH-3000 with a new impeller,

[Jeremy@CoralVue]

First things first. I would check the impeller. If it is a needle wheel I would suggest upgrading to the pinwheel that now comes with these skimmers.

The image below is the Pinwheel that I am talking about. If you don't have this wheel I would recommend getting it.


The model you have is pretty old but we can get it working like a champ. I also don't recommend feeding the skimmer via overflow. I say this for two reasons:
1. your overflows do pull the enriched proteins skimmed off the surface of your display but it also will pull in oils that accumulate as well. Oils disrupts the skimmers performance by changing the surface tension of the bubble surface.
2. Air often surges through an overflow as well as fluctuations in internal water level do to pressure changes of the water being fed to the skimmer.

To get the greatest consistency and performance out of your skimmer I would feed the skimmer from its own pump. I would steer for 1.5 to 2 times your system volume as a feed rate. Just one up the pump and place a valve on it so you have full control of the feed and output settings of the skimmer giving you the utmost control.

[boca rat]

Thanks for the prompt response

Pretty sure this is pinwheel but will check, which is of course a major PITA as have to completely drain or remove the skimmer to get it out, something that I hadn't factored in....

I don't understand the difference between water direct from the overflow, vs. water in the sump that comes direct from the overflow. Where do you think the oils are going once they hit the sump?

I was really hoping to avoid another pump but I guess I will have to give this a go or throw this thing out.

[Jeremy@CoralVue]

The difference is that with a pump you are feeding consistent pressure for a water supply. Feed from overflow is a gravity feed which will vary to drastically for a consistent level, its hard to tell exactly the amount of water you are feeding, air pockets can purge through the skimmer and more likely going to get something like a snail, shell etc from directly entering the skimmer. The difference with surface oils is that you directly introducing the oils from the surface via overflow feed vs than in a pump fed where the oils would have a chance to dilute and even resurface before it ever gets a chance to be pulled into the skimmer.

[Jeremy@CoralVue]

Also remember that I am just offering my opinion.

[boca rat]

)

Does make some sense on the dilution side, not so sure about the inconsistent feed on a minute by minute basis, if the feed up to the tank is constant, so should the return be (snails etc not withstanding) or my ATO would be very unhappy. I might try and run it for a minute or two without the OTH and look for air pockets as well.

I have a Mag3 that I could hook up as a test. Just a PITA to replumb it all.

Thanks

[boca rat]

OK, hooked it up, seems like bubbles are finer than before, but output similar, let me give it a day or two to bed in.

What should the ideal water level in the skimmer be?

[boca rat]

Also, can you tell me what the internal diameter of the airline should be? I am wondering if this got swapped out and is too narrow....

Thx

[jeremyblu]

Remove the line an run hot water through it. Make sure its not plugged at all.

[boca rat]

Done, no difference...( I know I checked the venturi when I set this thing up. Next step is to pull the whole thing out and remove the pump I guess....

[Jeremy@CoralVue]

I would give the skimmer some time to break in and re adjust after you re plumbed it. Any time you add new plumbing you will require some time to get back into operation. How much water are you feeding the skimmer now and what size bubbles are you seeing in the bottom neck area?

[boca rat]

Using a Mag 3, dialed back to about 50%. Bubble size is fine but not that fine. What is a typical water level in the neck? Will post a new pic shortly.

[Jeremy@CoralVue]

I suggest the water level never to be any higher than where the cup meets the body. Try to shoot for pea size bubbles or larger in the neck area and go from there.

[boca rat]

I took apart the volute (?) and find a white oring that is block about 70% of the two airholes. This is correct? I removed it and find there is a slow drip now.