Pros and Cons of NNR Plenum...?

[cashemin44]

My fiance and are looking into different types of filtration and we were wondering if anyone had a feedback on this specific kind of system? It's supposedly really fantastic, but we dont't really know anything about it. Opinions please

 

[coachklm]

Not Me ,Pulled from Web....
"Yes, I too have had an persistent algae problem while running a NNR plenum system. This occurred at aprox one year to 14 months. I “unscientifically” attributed the problem to detritus buildup and high nutrient levels. I then took the system down, re-setup with a bare bottom, raised rock system and the algae disappeared. I find this discussion very interesting regarding the “success” of this type of system. Can all this be a coincidence? I don't think so. This NNR as I understood it was to eliminate/drastically reduce waterchanges. A “too good to be true” system. NNR or natural nitrate reduction is, I would think, just what it says. We all know that nitrate will get reduced with the correct amount of “live” rock or sand in relation to the bio-load of the tank. It is my opinion using the *correct* amount will have a large role in the long term “success” of the aquarium. I use and recommend 1.5 to 1.75 lb. per gal. Using too much live sand or rock can trap debris/detritus going unseen and building up a food source for micro-algae as well as being unfavorably biologically dense for the enclosed system. In my system ( a55 gall) , the 1.75 “ aprox sand thickness came out to be 80lbs or 1.45 lbs per gallon. I also added aprox 50 lb of live rock bringing it to over 2.36 lbs per gallon. This leads me to believe that excessive biological medium ie:live sand or rock becomes “un-manageable” regarding nutrient build-up over extended periods of time. "

 

[turningtim]

The only contact that I have had with a Plenum is at my LFS. By watching this system for the last 2+ years I would never recommend it. I believe that as stated above that its just a place for things you don't want in your tank to stay there. I really see no advantage of a plenum over LR,LS and a corretly sized refugeium. The algae is out of control, it still requires the same amount of water changes. The water parameters are no better than the tanks that don't have this system.
Just with my limited knowledge/opinion its just a ticking bomb of toxic gas waiting to blow.
Besides all that its just flat out nasty looking!
JMO
Tim

 

[zman1]

Google = An Experimental Comparison of Sandbed and Plenum-Based Systems
For a nice 2 part article... Change the 6 to a 7 in the URL for part 2

 

[zman1]

I picked one of the overall summary bullet points from the part 2 page.
Overall death rates were roughly twice as high in aquaria with shallow sediments as in deep sediment treatments. The highest overall death rates were seen in aquaria with shallow coarse sediments over a plenum, and the lowest death rates occurred in aquaria with a sandbed composed of deep coarse sediments. The treatments that were closest to the design aquarists employ for deep sandbed, Miracle Mud and Jaubert plenum aquaria had intermediate death rates. The shallow coarse sediment design that is closest to that used in Berlin systems had one of the highest death rates, and the deep coarse sediment design for which there is currently no accepted name had the lowest overall mortality (Fig. 10). We did not test bare bottom tanks, but the data clearly suggest that the shallower the sediment, the higher the mortality rate, and you can't get much shallower than a bare bottom tank!