Mechanical Filtration Question

[SimonWoodstock]

I've read several things talking about mech. filtration for SW. I have come up with a few of questions, I hope i haven't overlooked the answers in another thread.

edit--*void questions 1 & 2...for now*

1) Besides using live rock for bio. filtration, do i need (would it be a good idea) to get something for mech. filtration?

2) If yes, then what is best canister or HOB?

3) Could someone explain this for me: I've noticed some people saying they use a filter w/ carbon in it so if the water gets cloudy they turn it on until the water clears up. What is going on here?

4) What does a skimmer "actually" do? I still don't get the whole concept, i just know i'll need one.

I still haven't made up my mind totatly for SW, I'm still trying to figure all this stuff out while keeping other options in mind.

Thanks

 

[Alastair]

I'll have a shot at #4 for you:

What it does:
Basically, a protein skimmer, also called a foam fractionator, is a device for seperating certain dissolved organic compounds from the water. In an aquarium, the idea is to remove organic material *before* heterotrophic bacteria can digest it into ammonia and thus bring it into the nitrogen cycle. The idea, therefore, is to reduce the organic load in the water, thus reducing nitrate accumulation and raising ORP. It will also -- to some extent -- remove very fine particles such as free-floating algae cells from the water. These microparticulates and organics are concentrated into a liquid effluent which can be easily discarded.

How it works:
Skimmer dynamics are pretty complicated, but here's a simplified overview. You may have noticed that an oily film sometimes accumulates at the surface of a fishtank. This film occurs because certain organic compounds are attracted electrochemically to air-water interfaces (ie places where air and water touch). A skimmer functions by creating a vast surface area of just such an interface, in the form of billions of tiny bubbles in a water column. This interface attracts the organics, which bond to the surface of the bubbles. As the bubbles rise through the water column, they drag the organics with them, until they reach the surface, where they accumulate as a thick foam. This foam gradually rises into a seperate compartment where it collapses into a thick liquid, which is the waste effluent.

Obviously, it takes time for a bubble to pick up its full "load" of organic material, and that is why taller skimmers, with longer "contact times" tend to work better. Also, more surface area = more stuff removed, which is why skimmers that make larger numbers of very small bubbles work better than those that make fewer larger bubbles.

 

[SimonWoodstock]

wow, great info. you explain things very well. i guess, in a way of speaking, the foam you see in the ocean and eddies in creeks is the same thing a skimmer simulates?...either way i see a clearer picture now....thanks!

 

[Alastair]

The foam formation is very similar to that you see in creeks or created by waves, yes. The difference, of course, is that in nature that foam usually just ends up getting mixed back into the water, so there is no net gain or loss of material. In the aquarium, you remove the effluent, thus reducing the overall amount present.

Glad this was helpful to you