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View Full Version : If your skimmer is too big...


JohnM99
09/07/2011, 08:23 PM
can you compensate by running it only a few hours a day?

Often people have plans for a larger system, but need a good skimmer until they upgrade - what do you think about buying a skimmer for the bigger system, and running it on the smaller system for say 12 hours instead of 24 hours a day?

My understanding is that if there is not enough material to remove, their won't be enough foam to fill the neck and rise into the cup - presumably if you only skimmed part time it would work - or am I out to lunch?

Thanks

Nitro069
09/07/2011, 08:28 PM
i am kind of curious to find out myself. i have a skimmer that is rated for twice my tank and find that it works best after it has been off for a bit. otherwise all i find it doing is making small bubbles that don't make it to the neck and throw "skimmate" back in to my tank instead of the collection cup.

jwalker314
09/07/2011, 11:04 PM
I am also interested....I have a skimmer rated for a 320 gallon tank on a 140 gallon setup. I let it run constantly. Maybe I shouldn't? Would like to see some pros to not running it all the time.

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tkeracer619
09/07/2011, 11:20 PM
Generally you just run it dryer. It takes longer for the foam to get into the cup and you get more crap on the neck but you still collect it.

I would try carbon dosing and feeding twice or 3 times a day before running it for only 12 hours. Mainly because of the air exchange the skimmer provides.

2_zoa
09/07/2011, 11:22 PM
Me........I would run the skimmer all the time. Or at least run it 12 hours a day.(Daytime)

I think if one were to run a skimmer they would want it in action to always be ready to remove what needs to be gone. Do you skim wet or dry?

2_zoa
09/07/2011, 11:25 PM
Generally you just run it dryer. It takes longer for the foam to get into the cup and you get more crap on the neck but you still collect it.

I would try carbon dosing and feeding twice or 3 times a day before running it for only 12 hours. Mainly because of the air exchange the skimmer provides.

Does it really? I have thought a skimmer didn't really do much for gas exchange because the interface is loaded with funk??

tkeracer619
09/07/2011, 11:29 PM
It absolutely does.

garrett3423
09/07/2011, 11:49 PM
the only problem you could incur from running a skimmer that is way too big for your tank is the removal of organic matter so fast that you can't get enough to your corals or other inverts that may need nutrients in the water column. however spot feeding corals can fix this, it all just depends on how you approach the situation and your tank specifically. what may work for one may not for another. Your skimmer wont produce that many bubbles because its already removed all organic waste from the tank but running it 24 hours a day is definitely recommended because of the gas exchange. besides there's nothing like an outbreak of algae to change your mind in a hurry. I run a marineland skimmer rated for 100 gallons in a 36 gallon system and it takes forever to fill up the collection cup, I just like how there's a bit less maintenance to do!

James77
09/08/2011, 08:01 AM
My understanding is that if there is not enough material to remove, their won't be enough foam to fill the neck and rise into the cup - presumably if you only skimmed part time it would work - or am I out to lunch?


That is what I have experienced with over sized skimmers. The most performing skimmer I had, an H&S, was on a tank exactly the size it was rated for.

When I had a greatly oversized one, nothing really made it into the collection cup, just stuck on the neck. It still removed stuff, but a skimmer will perfrom like crap with buildup on the neck. You want it going into the cup.

If you are planning a tank upgrade in the near future, i would not worry about it. But if it is more than several months ahead, I would just bite the bullet and get one sized for the tank....assuming it is a manufacturer that rates them appropriately.

brycerb
09/08/2011, 08:27 AM
Just skim a little wet, because unless you have it on a timer you will forget.

MagicReefer
09/08/2011, 08:31 AM
Keep in mind that you need to go pretty big to get no skimmate action (in general). My skimmer is rated for a 125 and i have a 57g tank.

I think it is the perfect match. I set it to a drier skimmate and it still pulls out plenty of nasty. This combined with the ATO, my salinity NEVER changes. I clean the skimmer during water changes once a week.

There is no notice to the corals in refrence to food either. Most corals can produce their own food through photosynthesis. There is a debate about pulling to much from the water with a bigger skimmer. I have not seen this side effect. My levels all stay on point and remain that way with water changes.

I would say as long as you dont go more than 4x the tank size you should be ok. remeber, not all skimmers are the same. Two different skimmers rated for the same size tank can produce two completely different results.

JohnM99
09/08/2011, 08:57 AM
My thinking on this is that the skimmer doesn't "know" how big your tank is - it just sees whatever water you give it. If you ran it for 1 hour a day, it would see lots of organic molecules in the water, attaching themselves to the bubbles. There is a limit of what a skimmer will remove - maybe about a third or so of TOC - as per recent articles - probably since the rest of the TOC are not in a form that will attach to bubbles. So, I would have thought it will run with good foam / crud production until the skimmable TOC was mostly reduced, and then it would run without much production, until the source water provided more.

So, if you ran a skimmer rated for say 400 g on a 100 g tank, but ran it only for 6 hours a day, would that be any different from running a 100 g rated skimmer 24 hours? I have seen people who say the same as James77 has said above - James, did you run that 24 hours a day? Did you try running it fewer hours?

Thanks everyone.

James77
09/08/2011, 10:57 AM
So, if you ran a skimmer rated for say 400 g on a 100 g tank, but ran it only for 6 hours a day, would that be any different from running a 100 g rated skimmer 24 hours? I have seen people who say the same as James77 has said above - James, did you run that 24 hours a day? Did you try running it fewer hours?

Thanks everyone.

I run all my skimmers 24 hours. The skimmer that was oversized was a Reeflo Orca 250 with the pump and neck upgrade. Maybe the skimmer just sucks, that is possible. It was running on a system with a 75 display and a 175 display and a small sump, I think it was a 40 breeder. The skimmer was rated for 200-800 gallons, but I would get nothing but heavy buildup on the rime of the neck. No algae problems IIRC, so maybe there was just not enough crap to be pulled anyways. The H&S I was running was with the 175 tank and a 55 gallon sump, the skimmate that mad used to lift the lid and cascade down the side, and I had no algae prooblems.

A couple problems I see with running the skimmer intermittently is most every skimmer I have had takes a little time to actually start working, its not instant skimmate when the power goes on. Also, when it sits for 18 hours, buildup in the neck may dry, and affect its performance. Then there are the start up potential problems. Just about every skimmer I have had has at least once not started up when first plugged in, and they were only stopped a couple times a month for maintenance...not daily.

LOTUS50GOD
09/08/2011, 12:26 PM
You should be able to tune the skimmer to fit your tanks needs.

Ducati 911
09/08/2011, 12:30 PM
I have a 20G with the AquaC Remora 1200 and pre-skimmer. I have it hooked up to my light timers because its in my bedroom and is too loud at night.

Turns on at 11am and off at 9pm.. seems to be working fine for me.

Prince916
09/08/2011, 01:54 PM
Many sps keepers use over sized skimmers to get low nutrients. As the nutrients gets lower then the heavy feeding comes in. Heavy feedings = more junk for skimmer to pull.


*but you can have a really over sized skimmer to a point that it wont pull any skimmate.*

jayg4u
09/08/2011, 01:58 PM
Twice is good, but if you go completely over board you may have issues. Better to run it dryer than on cycles.

Jeffo.it
09/08/2011, 02:13 PM
Many sps keepers use over sized skimmers to get low nutrients. As the nutrients gets lower then the heavy feeding comes in. Heavy feedings = more junk for skimmer to pull.


*but you can have a really over sized skimmer to a point that it wont pull any skimmate.*

I agree. I have a LGs800sp for aquariums larger than mine and this allows me a generous feeding of corals and a more equal balance between autotrophic and heterotrophic nutrition. Obviously, to avoid massive extraction of trace elements, my skim have to be dry.

Palting
09/08/2011, 02:26 PM
I would still run it 24 hours a day. I have a 150 gal tank, and a skimmer rated for 300 gal running 24/7.

The amount of foam in the neck has nothing to do with the size tank nor with the amount of DOC's. The amount of foam in the neck is determined by the settings of your skimmer and it's capabilities. It's the amount of skim that changes with the amount of DOC's and the size tank. If you don't have a lot of DOC relative to your skimmer capability, the example for an oversized skimmer in a small tank, then you won't make as much skim, that's all. But the amount of foam in the neck will be the same whether it's a big tank or a small tank

JohnM99
09/08/2011, 03:29 PM
I think the consensus is you can be a bit oversized and get away with it, but probably not more than 2x rating.

As for the amount of foam - I would not agree that foam production is unrelated to water content - although the bubbles are made by the skimmer by a variety of means, the surface tension of the water is very important in determining how long the bubbles remain as bubbles. The surface tension of the water is dependent upon many variables, one of which is the concentration of amphipathic molecules.
http://hyperphysics.phy-astr.gsu.edu/hbase/surten2.html
If you don't believe the formulas, just look in a hot tub that is clean versus dirty.

Anyway, I appreciate all the advice of such experienced aquarists!

ScubaPrawn
09/08/2011, 04:47 PM
Don't want to hijack the thread, but what companies are considered good at giving accurate ratings.

I'm considering a needle wheel Reef Octopus that's rated for 250g for a system that'll have roughly 150g of water

JohnM99
09/08/2011, 05:51 PM
I think Mojo over in the skimmer FAQ thread has very good handle on that - it certainly varies