protein filter for fresh water (piranhas)

  • We are currently upgrading MFK. thanks! -neo
I add salt only when ich rears it's ugly head, and then, only up to around 3ppt(parts per thousand). Sea water is @ 35ppt.
The 1st time I heard about protein skimming in fresh water, was in an article in TFH mag in the late 80s, called "Foam Fractionation in a discus Hatchery" by Joe Gargas.
Sea water is more dense, and that's the reason (I believe) the foam is so viscous, as compared to fresh.
But I've seen it happen naturally in rivers and lakes where foam builds up in protected bays after heavy wave action, or in spring when rivers foams up after winter.
 
Even an airstone produces smaller bubbles in saltwater. That's why they are more effective. If you were to attempt this I would advise getting a water pump that has a newer style impeller that further chops up the bubbles to kick start it. I might even go with a larger than suggesed pump. Turboflotors can be tuned down if pump overdoes it's job. The new impeller assemblies have different names from brand to brand but you'll see the "chopping" bit in the descriptions. I have never personally tried this on freshwater but as we can see it can be done. just my .02
 
Ullo, I believe that's very good advice.
On one of my skimmers I use a 2400 GPH mag drive pump, and a 1200GPHpump on the other. The venturi valve alone creates at least a 20% loss in pump pressure. In the article I got the plans from, Mr Meyer uses a 1 1/2" Spa jet (hot tub) venturi, and I had to scale down to a 1/2" mazzei to make it work in the basement tanks.
 
Ullopincrate;2859158; said:
Even an airstone produces smaller bubbles in saltwater. That's why they are more effective. If you were to attempt this I would advise getting a water pump that has a newer style impeller that further chops up the bubbles to kick start it. I might even go with a larger than suggesed pump. Turboflotors can be tuned down if pump overdoes it's job. The new impeller assemblies have different names from brand to brand but you'll see the "chopping" bit in the descriptions. I have never personally tried this on freshwater but as we can see it can be done. just my .02
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That is what was saying about modifying the impeller with some enkamat to get more bubbles. A lot of SW fish keepers modify their impellers to get more foam action.
 
What I think would be even better than an impeller addition, would be some kind of bubble slicer that could be added inside the column after the venturi. Because the column is where the reaction occurs. If the slicer could turn by flow action it may be more efficient, I worry about cavitation backup pre-venturi. Although I do not have an engineering abilty to know if this is true or not.
 
Cichlids dont need salt...it depends on where they are from.i have allways had mine on pure freshwater.

But now to the real issue of this talk.I have too being very interested in suing skimmer in a FW tank, and have being searching for information.And found it for a long time ago..it is a greek cichlid-page,with a lot of interesting articles about other things too.

http://www.malawicichlidhomepage.com/aquainfo/skimmer01.html

it describes how and why a skimmer works,and why it is less effective in FW,but it discusses the use of a skimmer in FW too
 
fracko014.jpg

fracko012.jpg

Here's the scaled down venturi tube
fracko001.jpg

fracko003.jpg
 
Thanks Zardoz, this article is just what I needed to read. It does say that a skimmer could be less effective in a FW setup but also says it can work when properly modified. He says putting an oversized pump can achieve this, I would just modifiy the impeller. Most skimmers nowadays come with nice decent pumps, all they need is a better/modified propeller to chop the water into finer bubbles. I also like the fact that he points out that a skimmer helps reduce the need for so much water changes. When I used to have my SW setup I would go like for two months without a water change and all I did was just replace evaporated water and replenish elements like calcium, magnesium, potassium, etc. and the tank would thrieve.
 
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