Very frustrated with 9410 skimmer

[Plainswalker]

I've had this skimmer for 6 months and it's been very inconsistent and generates a lot of splashing noise.

1. Inconsistent skimming - some weeks it will be skimming ok, then other weeks it barely generates any skimmate, regardless of feeding load - bad enough that I'm starting to have algae issues. I've made sure that the outlet tube is fully seated and that the collar for the filter sock is not over the end of the outlet.

2. Splashing noise - for some reason, the outlet (which is around the height of the water line) shoots out about an inch of water above the waterline, which creates a lot of splashing noise + salt creep in my sump. I've tried mitigating it by placing a coarse sponge with a hole in the middle (to avoid blocking the outlet) just over the collar, but that only reduces it.

I would live with #2 if it meant that the skimmer is skimming consistently, but it's been problematic. I do vinegar dosing, which means the skimmer is a very important part of my filtration, so I do want to solve this (or else get a different skimmer). I'm not sure if the 9410 is overkill for my size tank though.

Aquarium stats:
90g w/ 40g sump, 10 fish, heavy feeding
Sitting in 7in of water height

 

[rvitko]

We would rate the 9410 for between 80 and 265 gallons depending on load, the 80 gallon rating would be for an intensive SPS tank with a very high fish load.

Can you send me a photo of the unit as it is in the sump, a side view would be the most useful?

1) The inconsistent skimming could be related to food or additives, variation in water level or too low of a bioload (oversized skimmer). Foods which are high in fat (mysis and some pellets) can break down the foam column for a few hours. Additives like amino acids, vitamins, stress coats and medications (including reef safe and algae killing meds) can act like surfactants and affect the surface tension of the water changing bubble size and how far bubbles carry. If the skimmer skims well after cleaning or feeding when sufficient organics are suspended and then has a constant foam head but not enough to rise into the cup, it is likely oversized. For the purpose of our sizing, sump volume does not count, it is unoccupied additional water that does not add to the load. From a technical aspect the only causes would be a leaky silencer, fluctuations in water level, debris in the needlewheel or improper assembly of the outlet tube. I would remove the silencer (air hose assembly) and plug one end with your finger and blow in the other, make sure it holds pressure. I would inspect the needlewheel for algae and trapped debris, anything which would make it "larger" would increase the flow volume erratically. Make sure the water level is relatively constant and you might try lowering it about 1/2", a variation of more than 1/2" if sudden or 1" over a day could cause a dramatic change in performance. Make sure the outlet tube is fully inserted in the skimmer base and that the filter bag attachment is just a little below the top of the pipe so you are not raising the overall exit height.

2) This would seem to be related to too much water and not enough air. The skimmer has a self adjustment feedback loop, if the surface tension or water height changes or water is backed up from the exit due to a restriction, the water rises in the middle chamber, the water then is drawn into the silencer and cuts the air flow, this is meant to stop skimming if the result would be only clear water being removed due to a surface tension issue or installation issue. Any of the causes pointed to in (1) could have this result. Additionally starting the skimmer with the air closed can cause a very high water flow through, start the skimmer with the air open and adjust from their and generally it should not be more than 50% closed. As you decrease the air flow volume, the water flow volume increases. Lowering the water level or raising the skimmer will help. The pump can safely be run as long as at least 2/3rds of the motor (not including the air intake at the bottom) is submerged. When the water level is lower, the pump has to work harder and can pump less water for the air ratio.

 

[Plainswalker]

I took the pictures but I dunno what angles would work - please tell me if you need a different view:

From what you've described, it seems like my skimmer is oversized. My system water volume (excluding sump, rock, etc) would probably be in the 75-80 range, which is on the very low end of the 9410 range. My water level is maintained by a baffle so there aren't really any fluctuations to speak of.

I do have a foam head that makes it into the cup, but the skimmer runs very very dry (~ half a cupful per week). I will try raising the skimmer and opening the air, but it might be that it is just too big and I need to downsize.

 

[rvitko]

I am not convinced the issue is that it is oversized.

In the photo the water exiting from the hole in the skimmer body seems normal, when it is going crazy is this flow volume much higher?

The air looks to be closed an extreme amount, keep in mind that the pump essentially does 400 gph and what you set is the ration of air to water, if the air is closed substantially you get maybe 50 gph of air and 350 of water, if the air was all the way open you get 150 gph of air and 250 gph of water, this is important because overly restricting the air can greatly increase the water and cause issues with the operation.

 

[Plainswalker]

Just wanted to post a followup on this - Roger hit the nail on the head in that the air was closed to an extreme amount. Originally this was because anything more than 1/8 open I was getting a lot of foaming and overflowing. I guess this was because it was too new. I had assumed I cannot open it up any more.

I have now opened the valve nearly all the way, and it is now skimming more consistently and is quieter to boot. I waited a few days to confirm that it stays that way, and it is.

Thanks Roger, you were very helpful!!

 

[rvitko]

Great news, thank you!