Pros vs Cons: Wet Skimming vs Dry Skimming

[mila sheehan]

I don't have a skimmer and I don't really need it but wet skimmers sound more effective instead of the dry ones that will take more time.

 

[Crystalsreef]

I dont skim at all...i still dont even really know what its really all about. Would someone like to endulge me.

 

[Bruce Burnett]

I dont skim at all...i still dont even really know what its really all about. Would someone like to endulge me.

A skimmer uses foam fraction to remove proteins and other particulates before they break down into dissolved organic pollutants in the water. If you have been to the beach at the ocean and seen a thick foam it is the same process. It is not always needed depending on your setup and husbandry. Besides removing protein it can help export of dissolved organics by removing bacteria that consumes the dissolved nutrients. A skimmer will reduce amount of water changes needed and will also aerate the water before it is returned to display tank. Most people use a skimmer with other processes to export dissolved organics.

 

[aereaus]

Thats probably a fair assumption and one of the main reasons i think its important to run a skimmer thats rated UP to but no more than 2x the tank volume. It ultimately depends on the size of the tank though, at least i think. Smaller systems in my experience benefit less from larger skimmers as they dont usually produce the amount of waste so the foam usually just sits in the neck. However, on our 500g system we run a royal exclusiv alpha 300 and it does great. Not all skimmers are created equally though

 

[Randy Holmes-Farley]

maybe a stupid question but could you get the same effects of wet skimming by using oversize skimmer for the tank set to dry skim? I mean if your skimmer gph is close to your return gph you would be running more water through a dry skim not missing as much wouldnt you?

Yes, it is almost certainly true that a larger (more effective) skimmer will be able to offset (and probably more than offset) any reduced skimming action from removing dry skimmate vs wet skimmate.

 

[Bruce Burnett]

Thanks Randy was hoping you chimed in. I think an efficient oversized skimmer will have periods of no foam not because the neck is to large but because not much left to remove. If I feed my tank the skimmer will start foaming more about 20 minutes later and stop after about an hour. I found I had to feed the fish and corals more to have the corals keep their color. A smaller skimmer that never has periods of no skimmate means you are getting more imported than you are exporting if you stop feeding the smaller skimmer would eventually reach a point that it does not produce any skimmate but then you may starve your fish. It is my understanding that you want to remove what is not consumed before it breaks down.

 

[SaltyJD]

For me, dry skimming produces the best results.

 

[tjnorthdakota]

I don't see how a skimmer no matter the size could starve corals or fish, seems like something in the tank be it liverock, filter sock, sand, something will trap enough waste and food to provide the bacteria enough nutrients to complete the ammonia cycle to feed the corals. From what I know of skimmers they only remove organic molecules not in inorganic ones like phosphate and nitrate. I think it would be othe medias we use like phosban, gfo, bio pellets that would starve the corals

 

[Bruce Burnett]

I use gfo and pellets. The pellets are a carbon source that bacteria use. The bacteria will help to feed the corals but a good skimmer will remove much of the bacteria and export nutrients that are consumed by the bacteria. I have a bare bottom tank and virtually no detritus settles in the tank. So yes the combination can starve your corals and they will turn pastel colors and bleach if not fed. This would be much less likely to happen with a small skimmer. I am not a chemist but until I went to a much larger skimmer I never had to worry about corals needing additional food.

 

[tjnorthdakota]

I'm curious, do you use a recirculating bio pellet reactor where you can dose the drip? I tried pellets, never really liked them much but then I was using a cheap reactor I couldn't really control the output on.

 

[Mark Shelly]

Typically when one oversizes you adjust it for perfect skim, then after a while (hours to days) you notice the skimmer isn't producing anything at all!! So you adjust it a lot and raise the level. You then find it puking out the skimmer cup later.

This has been one of my biggest problem being a new saltwater aquarium owner with no sump, trying to find the best setting. I purchased an oversized HOB Reef Octopus for my tank. The local fish store said that they did not keep the next lower size because it kept overflowing (they have it now though). The larger one would overflow slightly every time it turned on unless I put a finger in and on one side of the return pipe. If I start the insert cup too high it scums up the throat and doesn't remove anything even when I lower the insert. If I start it with foam to the middle or top of the throat it will fill the cup very fast (and sometimes the insert will sink). I now find that if I keep the cup/insert bottom just at the water line in the etched portion of the skimmer body, it initially has bubbles in the lower portion of the neck but, builds up until I have fairly dry non-moving bubbles between the outer top edge of the cup and the lid as seen below. This is where it seems to work best, especially if I clean the cup every 4 days or so. This is probably just on the dry side.

I might mention a potential problem I have that everyone else might not see in the sump or with an overflow. The slots for the intake into the skimmer don't always get the surface film if the water level is near the top of the slots as seen below. If it gets too low, air gets sucked into the skipper water intake. So there is a narrow range of water depths that it works best. I don't like to turn it off a lot because of the overflow issue and because I believe it helps oxygenate the water, but I do at water changes. And like others have mentioned, top off water won't replace the salt from the wet skimmer and water changes alone don't account for the salt left by evaporation (minus salt creep).

 

[Bruce Burnett]

With my skimmer since it is large I adjust it so that it is as close as possible without putting straight tank water into cup, when I get nothing I don't worry as it will start again when there is more to skim. I was using the large phosban reactors for GFO, pellet and gac. I then went to a recirculating pellet reactor. I made too large a change on my GFO and almost killed a couple of frags. I switched to all in one pellets that way I am not changing out the gfo just adding to the pellets as they get consumed. I have my pellet reactor running almost wide open and must say there is more bacteria growth in reactor then with regular pellets.

 

[James605]

I try and stay alittle on the dry side. No reason really, just what I've always went for.

 

[Bato367]

How bout this, I use 2 skimmers, 1 dry skims and the other wet skims

That’s just rude.

 

[Mark Shelly]

Now that I have a skimmer in a sump, I thought I would add another perspective to the one above. I still find the new skimmer (Reef Octopus eSsence 130) takes getting used to as well (About 1 month). Unlike a HOB skimmer where the cup height and intake levels are important, I find the water level of it in the sump is the most important setting. You can set it up with a tube for wet skimming or leave the bottom open if it constantly overflows. This last I found useful for breaking it in. My sump is small (20 GAL) and I made it worse by placing a HOB refugium in the sump. The refugium dictates main sump water level. There was not enough room in the return compartment to take all of the tank water that drains down during power outages without raising the main sump water level. As a result, if the skimmer starts out low (deeper water) and fully open in the sump, it overflows upon restarting or when I change filter socks. I looked for a delay socket, but did not find on (Anyone know of one?). DC return pumps take a while to get the flow going at full level. (p.s. I no longer use the feed mode, but dial it back so it no longer syphons quietly and does not dump as much water back into the tank. The net result is that the entire contents of the skimmer end up back in the sump. I raised the skimmer to the lower water setting where I can get bubbles in the lower neck. The scum collects on the neck and slowly in the cup, which is bigger than the last. While I wish the body was an inch taller with the intake an inch up (to reduce microbubbles when close to fully open), keeping the skimmer in more shallow water reduces the overflow time, allows small adjustments for when I turn off power on purpose, or when I change filter socks (I get water from the inside of the sock into the tank when I change them). I no longer have to lift the skimmer up in the tank when restarting for a minute or so. I also use filter media in mesh laundry bags to control the skimmer height. I can wiggle it a little so the feet dig in for fine adjustment.
I am showing the sump with the skimmer deeper in the water which I do not recommend for a sump like mine which is undersized and packed. Note that the water level in my sock can get a few inches above the sump water level before it overflows. This is not an example of a good sump, but a sump that would fit my stand and refugium.

 

[Charles4400]

The refugium dictates main sump water level. There was not enough room in the return compartment to take all of the tank water that drains down during power outages without raising the main sump water level. As a result, if the skimmer starts out low (deeper water) and fully open in the sump, it overflows upon restarting or when I change filter socks. I looked for a delay socket, but did not find on (Anyone know of one?). DC return pumps take a while to get the flow going at full level. (p.s. I no longer use the feed mode, but dial it back so it no longer syphons quietly and does not dump as much water back into the tank. The net result is that the entire contents of the skimmer end up back in the sump.

I know the apex controller can help you with that. I have mine programmed to whenever the return pump shuts off (from power outage or manual) the skimmer does as well and will automatically turn on 10 mins later to prevent the exact overflow and dumping of skimmate you are talking about. (10 mins is overkill you dont have to set it this long).



I prefer a dry skim.

 

[Mical]

+1 on dry skimming