filtration question

[manzillo11]

are there any benefits to filtering the top of the water rather than the middle or bottom? im about to start a 29 gallon fowlr tank and i notice a lot of larger tanks (75g and up) have a built chamber that takes the very top layer of water into a seperate chamber and then usually down to some sort of filtration device below the tank. for my tank i bought a regular hang on the back biofilter and also a filter cartridge that attaches to my power head. as of this moment i have no way of filtering the top of my water. do i want to try and filter the very top?

thanks for any info
marc

[skeeter_ca]

One of the main reason you should draw water from the top is to breakup and keep a film from forming on the surface of the water. This film if formed will inhibit the O2-CO2 tranfer. You don't have to draw from the surface, but if you don,t you should have some type of agitation to keep the surface film from forming.

[kau_cinta_ku]

what aquadw is about the best way to answer it:D the surface that creates the film would be basicly like putting suran wrap over the top. it will not alow any air to exchange. having it run through a overflow box down to a sump helps in 2 ways.
1. it skims the surface to keep it clear
2. having water rush down to the sump will create more o2

[manzillo11]

any ideas on how to recreate this for a hob filter?

[slapshot16]

You need a skimmer box to slip over the intake. There are many on the market and also I have seen several DIYs on this website.

[manzillo11]

something like this?

http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=4423&Ntt=skimmer&Ntk=All&Ntx=mode+matchallpartial&Np=1&N=2004&Nty=1

hope i dont get in trouble for posting that.

[skeeter_ca]

Yeah that would help. Also you can direct the water return for the HOB above the water line and it would splash alittle to help keep the film broken up. The biggest problem with that is you will have alot of salt crip.

[manzillo11]

salt crip?

[skeeter_ca]

:D Crip, cripe, krip, creep, however you spell it. :D Salt will buildup in your canopy when the water dries from the splashing. Next thing you know the inside of your canopy, lights, cords, hoses are all covered with salt.:D

[skeeter_ca]

BTW, i'm the worst speller in the world along with being a two fingered hen-pecking typist. It takes me forever to make complete sentences.

[manzillo11]

its cool, i just never heard the term befor, this is all new to me, thanks again!!

[TracyJean]

I had a fowlr tank set up for 4 years with only hang on filters. I had 2 of them on my 55g tank. I never had any problems. The hang on filter would return the water at the top of the tank so there was plenty of movement. No surface film ever developed.
I have set it up again since we have moved and it is going to be reef this time so I've added a sump w/ skimmer.
IMO it depends on your budget and your plans for the tank in the future.

[skeeter_ca]

Yeah, i used the a 30gal FOWRL. Used a power filter (PF) and i noticed a film would build up on the other side of the tank from the PF. The PF would'nt stir the water enough on the surface of the whole tank. I also had a nitrate problem to then. Maybe that was part of it.