How should a good skimmer work?

[txaggie09]

I feel stupid asking this but curious as to how these things are supposed to perform.

I guess it would be easiest to describe what mine is doing and see if this is what is considered normal. I dont know what the design is called but my skimmer has an external air pump pushing about 48 lpm of air and a 900 gph water pump. I know this is an older design but i havent heard anyone complain about the performance and to be honest, i wasnt too pleased with my needle wheel reef octopus.
During the day the bubble column is pretty low in the collection cup, almost barely visible. At night, at some point (i have yet to see it happen), it will fill the collection cup with a very light skim, and it has a very large collection cup. The skimmer has been running for about a month now, so I would think that it would have broken in by now.

Tank info: 120 gallon, 55 gallon sump. Foxface rabbitfish, clown fish, six line wrasse, orange spotted goby, snowflake eel, and a flame angel. Also have a few acans and mushrooms.

I was always under the assumption that the skimmer would be skimming all day. Or at least most of the day, I know feeding and sticking hands in the tank can disrupt the skimmer. Is this not right? I would like to start pulling out some better skim. Ive been having to do quite a few water changes to keep my nitrates in check (although part of that was a prefilter that i forgot to change out some time ago, but still i think having the skimmer working better would help).

 

[jerpa]

A little more info about your skimmer or a picture would probably help with recommendations on how to improve its performance.

My skimmer, SRO xp2000ext, does seem to produce the greatest quantity of skimmate at night but I also feed frozen food right before lights out. It will often idle most of the day but what it does produce overnight is coffee colored funk.

 

[txaggie09]

Thats good to hear. I think with some finer tuning i can get some better production at night. Just didnt think it was right for it to produce mostly at night.

Skimmer is an Oceans By Design signature series skimmer.
here is a link, http://oceansbydesign.com/product_info.php?cPath=22_40&products_id=44

 

[viggen]

Has it always acted this way or did it take a week or two for it to start only producing skimmate at night?

From what I have read..... If a skimmer is properly sized it will not produce skimmate all day long. It will go in rest periods where the foam is low and nothing is produced. Then once their is enough stuff for the skimmer to pull out it will be able to pull out that amount over a short period of time

When skimmers are undersized, the skimmer will be working all day and every day and still never pull all the crap out of the water. Throughout the day it will be making skimmate...... My 15yr old euro reef clone falls into this category. I fill the 12in dia cup up every 3-4 days with black nasty stuff. I plan on getting a larger skimmer

Some state you can never over skim due to the skimmer kinda resting when it can't pull out anything else..... Which seems to be what your skimmer is doing.... Others state going with to large of a skimmer is really bad. I think over sizing like what I think your are experiencing is the best way to go. That way if there is a major die off or other issue that arises the skimmer can easily stay ahead of the problem at hand

 

[jerpa]

I wouldn't be surprised if that skimmer was idling on your system. I'd probably adjust the bubble column a little lower to get darker skim so it doesn't fill the cup every night.

 

[txaggie09]

Has it always acted this way or did it take a week or two for it to start only producing skimmate at night?

From what I have read..... If a skimmer is properly sized it will not produce skimmate all day long. It will go in rest periods where the foam is low and nothing is produced. Then once their is enough stuff for the skimmer to pull out it will be able to pull out that amount over a short period of time

When skimmers are undersized, the skimmer will be working all day and every day and still never pull all the crap out of the water. Throughout the day it will be making skimmate...... My 15yr old euro reef clone falls into this category. I fill the 12in dia cup up every 3-4 days with black nasty stuff. I plan on getting a larger skimmer

Some state you can never over skim due to the skimmer kinda resting when it can't pull out anything else..... Which seems to be what your skimmer is doing.... Others state going with to large of a skimmer is really bad. I think over sizing like what I think your are experiencing is the best way to go. That way if there is a major die off or other issue that arises the skimmer can easily stay ahead of the problem at hand

I cant say that it has always been doing this as before I was constantly adjusting the flow to keep the bubble column up. This would obviously cause it to go nuts at night, or whenever it actually had something to remove. With advice from OBD i set the flow at a suggested starting point and since then I have noticed this behavior. I am still in the process of making the fine adjustments to get some better production when it does skim.
This skimmer is certainly sized for a tank larger than mine so it is probably "resting" more than it normally would. Again, glad to hear that rest periods are a normal thing. I feel much better about this skimmer now.
From talking with OBD, the skimmer isnt too overrated for my tank. In fact, they recommend it for a heavily stocked 75 gallon up to lightly stocked 240. I think mine is on the low side of being right inbetween those 2. I guess I will just need to play with it some more and get it dialed in.

I asked OBD directly about this issue and this is their response. (its not that I didnt believe them, I just dont have much experience with skimmers and felt it was a good idea to ask for an outside opinion on here. Let me know if what they said sounds correct to yall).

"txaggie09 you have to look at the skimmer as a mechanically constant thing. It pushes the same amount of air and water during the day as it does over night. What does change from lighted periods to dark periods is the chemistry in the reef tank. In the evening you will get more blooms in regards to algae and bacteria, also you will get more spawning in regards to snails, worms and similar. During the day you will get more organic uptake from the critters in your tank that use photosynthesis, such as corals and higher form algae's.

The difference. This skimmer is designed to maximize contact time while providing the required amount of air mix required to break down protein chains, mechanically cleave dirty water moles and then chemically reattach them to clean air bubbles. So a simplier way of saying that is that most skimmers dont have the contact time or bombardment rate required to actually PROTEIN skim and instead (because the supply air and water from the same source and are dependent on each other) so they basically freight train the foam and just particulate is carried out to the skimmer bowl. Because this skimmer has the contact time and the correct bombardment rate not only will it carry the particulate out via the foam column but it will have the time and process to break down protein chains and dissolved organics that are in your water column. The reason you are seeing more foaming at night then during the day is that the tank is producing more dissolved organics and proteins (as reasoned above) during the dark periods.

The fix. So what we know in your case is that their are alot more organics and proteins available to the skimmer during the dark period as seen by the reaction of your skimmer. With that you want to adjust the water level in the skimmer so that it does not overflow in the evenings, a good starting point is to have the water level just above the black ring at the base of the fluted portion of the skimmer, and then work from their. Eventually the skimmer will reduce the amount of proteins and dissolved organics from your tank and you will see a balance in your skimming between light and dark periods.

Other things to note. So in your reef you feed the fish and so on, the food you feed will first kill all skimming as the oils will not allow for the formation of surfactants that allow a bubble to form (same will happen if you put your hands in the tanks). It takes a bit of time for this to pass which makes it slightly inconsistant, also those foods that are not eaten and the poop (which is 90% of what the fish eats) the fish generate during the day will take time to be reduced to a dissolved state (so more in the evening) which will add to the equation. Also in the evening when the lights turn off your going to get a massive change in photosynthesis, as in very little during the dark period, this will reduce the oxygen production and lower your ph. This will also have an effect on how things work biologically in the mixing chamber of the skimmer.

So bottom line, adjust your skimmer to make it so it does not overflow in the evening. As time goes by the skimmer will reduce the overall organics and protein level in the tank so that their is not such a big jump from lighted to dark periods and from their you will not notice a big change in production during the evening (unless of coarse you have spawning events)"

 

[Timber77]

mine always has a baseball sized head on top of the skimmer cone , as soon as food hits the tank it starts getting darker and can see it draining down to the bottom of the collection cup, a few minutes later it still has a white foam head up top

t5000 aquamedic on a 250 gallon mostly lps tank which is way overstocked with fish.