Newbie Q's - Protein Skimmers

Hey there. I've been looking to put together a sump/skimmer for my now cycling 75g. Just had some questions:

1) Flow Rate. Should it be fast to increase turnover? Or slow to increase bubble contact time?
2) What is the best, or preferred, method of aeration?

I was hoping to split my line from the tank to skimmer/sump, and then simply gravity flow through the skimmer into the sump - so I had ruled out Venturi, and was leaning to wood diffusers. Would this lessen skimming ability?

Thanks in advance,
Tristan

 

Wood diffuser style skimmers are productive in Counter current setups. Do you have space for a 4 ft tall skimmer? Otherwise I think you would be good to look at a Recirculating needle wheel skimmer. That would allow a flow through rate that is seperate with the pump producing bubbles. I am a fan of running water directly to the skimmer for the tank but know that most skimmers are best off at a flow through rate of 1.5 times the total volume. Thats probably around 200gph for your setup. I doubt that would be acceptable for the sump. You might look into routing some of the water from the overflow past the skimmer directly to the sump.

 

Good Questions

There are many theories like Scott said Counter current skimmers tend to be very tall. Your Idea of splitting your overflow water is a good Idea for use with a recirculation skimmer. You can also modify a ASM or Octopus skimmer to be a Recirculation.

J

 

With my current stand design, I may be able to use a four foot skimmer. If I can do this, would a counter current wood diffuser skimmer be as productive as the recirc needle wheel?

I was planning on splitting the line from my overflow and regulating flow to the skimmer with a ball valve - the ultimate flow into the sump would be regulated by how quickly my return pump was pushing water back into the main tank - correct?
Re: 200gph for the sump - I'm guessing that's too low? I was thinking of turning the sump over roughly 6/7 times total volume per hour, by means of the split overflow line.

Is the point behind recirculating flow in the skimmer to give added contact time w/o increasing the height? I don't suppose running through a pump would "disconnect" dissolved solids from the air-bubbles?

Again, sorry for the barrage of questions.

Thanks a ton.

 

The main point behind recircs is so that you can use a big pump on the skimmer to introduce lots of air while still having a reasonble flow through rate.

I would say that a 4 ft CC would be as good as a NW. Especially if you use a good air pump like an Alita.

 

Needle Wheel Skimmer Theory

Some of the theory with a needle wheel is that the recirculated water is already relatively 'clean', so the bubbles you're adding flow upward through the water that has yet to be cleaned, absorbing DOCs as they rise, and the water falls. (concentrating the dirtier water near the inlet/riser tube) If designed properly, no bubbles will be inhaled by the needle wheel, and so the concern about "chopping up" bubbles that have already been loaded with DOCs is somewhat of a bunk concern.

I'm in the process of designing such a skimmer right now, and I've read that the most time consuming DOCs can take 2 minutes to fully attach to an air bubble, so that's a good target for your flow through rate if you want to make sure your skimmer is being as effective as is possible.