Micron filter for nannochloropsis

[WDLV]

I was thinking a couple weeks ago about the prospect of filtering water in a fry growout tank by using a U-tube with a filter on both ends. The idea being to allow ammonia, nitrate and phosphate to be filtered via diffusion into the parent tank without the prospect of losing fry, rotifers or nanno while also preventing any copepods from passing into the fry tank. I figure this could be done so that a high density of rotifers could be maintained by us working folk who have 9-5 jobs and cant check on the densities every couple hours.

What size filter would be needed to prevent the nanno from passing through but still allow diffusion of molecular compounds?

 

[dave willmore]

I was thinking a couple weeks ago about the prospect of filtering water in a fry growout tank by using a U-tube with a filter on both ends. The idea being to allow ammonia, nitrate and phosphate to be filtered via diffusion into the parent tank without the prospect of losing fry, rotifers or nanno while also preventing any copepods from passing into the fry tank. I figure this could be done so that a high density of rotifers could be maintained by us working folk who have 9-5 jobs and cant check on the densities every couple hours.

What size filter would be needed to prevent the nanno from passing through but still allow diffusion of molecular compounds?

Walt, I'm not fully understanding your post so forgive me if I get something wrong. I assume your fry growout tank is at the same water level as the parent tank and the u-tube is an "equalizer" in keeping levels identical? If so, you'd need some type of pump to flow water from one to the next. Most phyto tends to be in the 2 to 20 micron size range, whereas rotifers tend to be in the 60 to 250 micron range. copepods differ depending on the type, but tend to go from the 50 to 800 micron range, maybe bigger with some species. many copepods eat rotifers.

Am I to assume that you're using a slow flow pump to send parent water into the fry tank, and then using the U tube to return it via gravity? If so, you need to filter water before it gets to the pump. I don't really see the need to filter both sides of the U-tube, you can just filter the side that is in the fry tank.

There are a number of issues regarding a filter that will keep in nanno but allow molecular diffusion. The only filters this small that I can think of are the membranes for RO water, activated carbon, and diatomaceous earth. If there is any water flow at all, the flow will tend to suck your nanno phyto into the filter media where it will die. And larger plankton like rotifers will also be held against the media where they will be trapped.

It would be possible to use a high surface area filter like a pleated cartridge filter and a slow flow pump to keep the suction pressure from damaging plankton. But I think it would be a more practical bet to filter the incoming water before the pump and understand that some of your phyto and rotifers will overflow back to the parent tank.

Hope I understood you correctly.

 

[WDLV]

Close... There would be no pump; just straight difusion. The molecules should seek equalibrium. I just needed to know the right micron size to keep the algae on the right side.

 

[dave willmore]

Then my honest opinion is that while diffusion will occur, it will occur in such a small amount that it will do little good to balance metabolites in the fry tank. Like one tenth of one percent small.

On the other hand, you could put a very slow drip from the mother tank into the fry tank and achieve more. You'd be bringing in high quality water and washing out the high nutrient water that invariably occurs in fry tanks. A low flow wouldn't trap your phyto into the U tube. and if you prefiltered the flow with 40 micron screen, you wouldn't be bringing in any copepods. Better yet, prefilter with 100 micron screen and bring in pod nauplii to feed the clowns.

clown survival rate goes up many fold when pods are included in their diet. the rich waxy esters and lipids of pods are far more nutritious to fry than rotifers.

Matthew Wittinrich wrote a very good recent book about marine larviculture and one of his strategies was to pack as many rotifers, pods and algae into the fry tank as possible so that nauplii would be in sufficient quantity for the fry. granted this strategy is better for the difficult pelagic spawn than it is for clowns, but the theory is a good one for clowns too.

 

[WDLV]

Good thoughts. Thanks for your input. I need to read more of M.W.'s book. I bought it recently and forgot I had it. I have a friend who raises pods. I will keep it in mind.

 

[Fishbulb2]

I've had this idea for awhile as well. Straight diffusion to move ammonia and other waste away without filtering out larvae or rotifers. However I had a slightly more complicated idea than the U-tube method. The diffusion rate should depend on both the surface area and concentration difference right? So I would drill a hole through my larvae or rotifer set up and install a PVC pipe basically running through this tank. Then the pipe would have very large sections cut out of it and sealed with 1 micron mesh or so. Filtered water would be run through the pipe and back to a filter placed at exactly the same height. Autotop off could occur in the filter as well. This set up would have no net flow of water across the mesh so you won't be actively pulling anything from the culture system into the filter. Filtration would be active and the water exchange would be passive. Plus by circulating water through the large surface area mesh pipe, you should get slightly more efficient filtration through diffusion I think.

Any thoughts?
FB

 

[WDLV]

Good idea... increased surface area.

 

[dave willmore]

Then the pipe would have very large sections cut out of it and sealed with 1 micron mesh or so. FB

I don't remember the smallest mesh sizes available but I don't think you'll find much under 30 microns. There probably won't be anything nearly as small as 1 micron. Even the small mesh sizes are 80% fabric and 20% opening, because the weaved material simply isn't fine enough.

You are welcome to use the finest mesh supply you can find. Aquatic eco systems and Florida Aquafarms are two suppliers that come to mind. But my honest opinion is that without some kind of slow flow, the diffusion theory will not process even one percent of your water volume. I don't mean to put cold water on any creative idea, so maybe you can create a solution around these thoughts.

 

[WDLV]

Found it in under 2 minutes.
http://www.filtersource.com/Polyester-Filter-Bags-c28.html

The flow could be done with a LiterMeter pretty easily. The complication being that I'd have to use mesh on both sides to prevent anything from passing over to the fry-side that would prey on the rots or choke the fry.

 

[Fishbulb2]

Neat. I would have looked into semi-permiable membranes but that looks like it might work fine. Are you sticking with the U-Tube strategy or what's your design now? I still think you want maximize surface area and move water across the diffusion barrier to optimize it. Give it a shot, it's a cheap experiment!

FB

 

[Fishbulb2]

My excitement made me double post.

FB

 

[WDLV]

RO membrane or the sausages they use in bio 101 were my initial thought but then I remembered that RO is one of the ways desalination plants purify drinking water. So that would keep in the molecules I want to remove. So I figured it would have to be a screen of some sort.
I think the final design will split a ten gallon in half. The U tune would go on the back of the tank and a bulkhead would go through the divider. Silicone would be used to seal the mesh and the pipe frame work would need to be needlepoint mesh or a similar material.
Keeping it unclogged will either require a cleaning regimen which could simply be cleaning after meta or backflush.
I could also just plumb the tank in and make the stand pipe in the larval tank half height of the parent tank... Thus allowing the waste to be returned to the sump. In that scenario, I could simply replace the stand pipe once the babies were large enough for full flow.
I'm saying "were" and "could" because I don't currently have any spawners and I'm planning my rack for optimizing space and maximizing larval survival.

 

[dave willmore]

Found it in under 2 minutes.
http://www.filtersource.com/Polyester-Filter-Bags-c28.html

The flow could be done with a LiterMeter pretty easily. The complication being that I'd have to use mesh on both sides to prevent anything from passing over to the fry-side that would prey on the rots or choke the fry.

Great job, and I must admit to being wrong. Kudos to your researching skills!

 

[WDLV]

I love Google!

 

[WDLV]

I think this is about dead, as all my questions have been answered. Thanks to you all for your help and ideas!