Could someone explain why exactly this is?? (Skimmer question)

[flyyyguy]

Why does my BM 250 skim better if I restrict the air back to 75%

I noticed a week or two ago that when my cotton in the air silencer creeped up and got clogged right at the opening with crap it pulled in fromt he air that it seemed to skim better.

So I installed a air valve off the end and played with it for the last week.

No doubt in my mind it is pulling even more crap out than it usually does restricted like this, so I will continue to do so, but I really want someone to explain the how and what is actually going on that could make less air more effective than more.

Thanks :)

ps- with that air valve coming off of the silencer it sounds like a fricken tank. Should I splice the two lines together somehow and put the valve before the silencer, or put a valve on each air line before the silencer or is there a better idea??

Or am I nuts and something else is going on entirely........less air is NOT really helping??

[Conky]

By restricting the input of air, you are allowing smaller bubbles to be formed. Smaller bubbles=more surface area for charged pollutants to adhere to. Big bubbles are not nearly as effective...at least that's my understanding/experience

[CruzinKim]

Finer bubbles form a better and more consistent foamhead.

[hahnmeister]

That could be the case, but from my experience with these pumps, I dont think that there should be a huge difference in bubble size as these threadwheels seem more than capable of handling/blending all the air they can draw in. It just doesnt seem like it would be 'enough' is all Im saying... not significant enough to overcome the lowered air and increased turbulence.

Really, with less air intake, that means that there is more water intake, so there should be much more water turbulence... which should work against you.

But then I realized something... if you didnt adjust your outlet level (either gate valve or standpipe), chances are that with the air decrease, the water intake increased, and your water level became higher in the skimmer. And that would make alot of sense... you got more skimmate because your water level was higher. Just another possibility. If anything, get it up to full air intake and raise your water level, and see what happens.

[GSMguy]

NM

[flyyyguy]

hanmeister. I was taking into account the wetness of the skimmate when I said it was pulling out more. It actually didnt visibly change in color or substance.

Thats what made me wonder if there was something else??.

It must be due to finer bubbles although they arent visibly smaller, and I have found I prefer to skim kinda medium with this skimmer, unlike the wetter skimming I have preferred with other skimmers

to be sure......its not like it made a huge improvement, but it was improvement nonetheless.

[Reef Sponger]

I've seen posts on lots of BM200 that show dramatic improvement with an air valve to control the air draw. Not sure why, but the bubble size is a noticeable difference with restricted air.

[flyyyguy]

So lets assume it is simply finer bubbles, evne though I cant visibly tell, no one has had any other suggestions.

Is there any modding I can do to the pump or mesh that would help my cause?? I.E. make the bubbles finer without restricting the air?? That seems like what the goal should be, instead of reducing the skimmers true potential by tapering it back.

Anyone??

[Percula9]

By causing the restriction, it causes an increase in the velocity of the air. Since the air is coming in faster it slams into the water harder, so making the bubbles smaller. It's based on the bernoulli principal. The air must speed up in the restriction.

[happyface888]

This is interesting does this apply to all skimmers?

[Percula9]

It applies to any venturi that draws air into a skimmer.

[USC-fan]

sound like the skimmer's water level is too high.

[flyyyguy]

<a href=showthread.php?s=&postid=10971723#post10971723 target=_blank>Originally posted</a> by USC-fan
sound like the skimmer's water level is too high.

???

Out of curiousity, how exacty does that prognosis relate to anything we are talking about here??


If you are referring to the water level controlled by the gate valve it really makes no sense .........Medium dark skimmate both before and after restricting the airflow. Pulling a ton of crap out in both cases, but a little more so when i restrict it. So too high of a water level controlled by the gate valve isnt it.

If you are referring to the water level in the skimmer section of my sump that couldnt be farther from the truth. Now if you said it was sitting in not enough water, that could possibly be a conversation, as in playing with the skimmer for the first couple of months in different water levels, I ended preferring it in 6.5" of water which is definitely on the low side of what most people keep the bm250 in.

[USC-fan]

i'm talking about the water level in the skimmer. If the water level is too high, the skimmer will not be able the max amount of air. Seems like you are just skimmer wetter.....

If you like the skimmer set up this way, then run it like that. :)