YADAYADAYADA Posted February 8, 2004 Share Posted February 8, 2004 Hello: I am puting together the pieces for my 20 gallon high tank with a ten gallon refugium. I have been reading about plenums and seem to be more confused than ever....some like, some don't and the reasons seem to be valid on both sides. I am thinking about going with a DSB in one tank and a plenum on the other. If I do this where should the plenum go in the tank or refugium? I am also thinking of putting a PVC pipe down to the plenum and leaving it in place but capped just in case I need to suck it out if things get screwy ( animal dies down in the oxygen depleted zone ) fouling things up. Equipment so far: Tanks of course, may lose the 20 high for a 15 gallon Mag Drive 500GPH pump, hopefully to use 1/4" barbed nipples to jet the water around in the tanks to keep me from using power heads. JBJ Formosa 24" light 130Watt, I know I am going to trick it right out of the box with at least another 65 Watt PC No light for refugium yet any suggestions? Johnny DIY rock soakin' in the tub. Link to comment
bobbyb323 Posted February 10, 2004 Share Posted February 10, 2004 Plenum have been out for years, they are dangerous! NO, NO, NO , a thousand times NO! Link to comment
tinyreef Posted February 11, 2004 Share Posted February 11, 2004 i don't know if they're dangerous, more likely if you don't set it up correctly they'll function incorrectly. goemans book is very good in laying it out but his recent position on them sometimes seems to lack the confidence he once had in such systems. (mebbe it's just how i'm reading him, i dunno) the escape hatch tubing you suggested doesn't sound too bad. i once discussed such a 'landfill de-gassing' method with tangster (formerly of about.com, 30 yr. reefer). he's an ardent anti-sand guy tho so he wasn't too keen on it anyways but he felt it could resolve some issues altho it would look fugly. if you do go with one i would opt for the refugium just in case you need to pull it. my plenum worked fine but i tore it down to upgrade tanks (5g -> 15H). hth Link to comment
onthefly Posted February 12, 2004 Share Posted February 12, 2004 I've had a plenum on my 45 for 6years now. As previously stated, if you set it up right.....they work! I think a DSB in a 20H is a better way to go....forget the plenum. Link to comment
KrackerG Posted February 12, 2004 Share Posted February 12, 2004 plenum? is that when you use "stilts" of some sort to raise the LR up off the sand? sorry for the noob ques... Link to comment
onthefly Posted February 12, 2004 Share Posted February 12, 2004 Sort of....a plenum is a "void" under your sand. To work, it must not have any direct flow from the main body of water. That way is gets depleted of oxygen and certain bacteria use NO3 as a source of O2 and release inert N2 gas as a product. They, along with DSB, have been debated into oblivion recently. Link to comment
wetworx101 Posted February 13, 2004 Share Posted February 13, 2004 I am in the plenum club. The problem with plenums is you pretty much need a 20Long to make them effective. The micro-currents needed to drive a plenum are created by the thermal differences that larger areas develop...ie, a 10 gallon sinply wont develop alot of micro-currents to keep the bed flowing. I am also very much against DSBs. Call me odd, but I am. There are some serious complications with a plenum, and you have to know how to deal with them, so I would not attempt to do one on a nano until you can handle it on a larger scale, and I wouldnt do it at all until you have many years of reefing under the belt. Unless, of course, you have a degree in marine biology or organic chemistry and understand whats going on in there. BTW, if something dies in a plenum, do you know what happens? Nothing. Its the whole point of a plenum. There are some serious long term side-effects with plenums you have to deal with, and have to judge if using one ir even worth it. Sure, if might allow you to quit using a skimmer and not change the water as much (if ever), but is it worth it? You tell me. I just like to watch the critters that the plenum tank has in it. I currently use a plenum on a 60gallon, the plenum is a 45gallon XL, thats 48"Lx18"Wx12"H...made by great lakes aquarium. It is plumbed in so if for some reason it starts to go toxic (1.5years, knock on wood) I can disconnect it. It is pretty much a short 75gallon. I use eggcrate to support the bottom and then a layer of fiberglass screen. On top of this I put 5mm arag 2" thick. On top of this I put another layer of fiberglass screen. This prevents the critters from getting down too far and disrupting the plenum. Then I have another 3" of 2mm aragonite. To this I seeded with about 8 pounds of live sand, arag-alive type as well as rubble containing critters from the LFS. I also added detrious packs after a few months of being set up. The critters are what I dig about the plenum tank. I keep the plenum dark pretty much all the time, but have a flo strip I can turn on to check in. I have a brittle star in there that must be 12" wide!!! The critters are key. It seems that most of the tests I see where plenums fail are because the substrate isnt being 'tilled' enough to keep the crap from just making nitrates and phosphates on the surface (it seems most of the testsing I see doesnt involve the use of sand sifters at all, just stagnant sand). The flow into and out of the plenum tank is very low, about 100gph, and lighting is kept off the sand all together. This seems to keep the critters doing their job more, as well as keep the oxygenation content of the water low...to prevent aerobic bacteria from forming, as well as prevent algae that would make oxygen. There are still some problems I have had to deal with. One, it the eventual buildup of chemicals in the plenum. For this reason, I drilled a tap into the bottom of the tank so I can drain the plenum once a month a little bit. This is done to drain out any buildup of chemicals before they go back into the system, and is done in this manner to prevent oxygen from getting into the plenum by other more invasive methods (it also provides a little micro-currentt surge...doing this mixing of the plenum could also be done with a magnetic scraper that gets used as a stirrer to keep the plenum circulating, I didnt have a chance to get this under the plenum before starting this time, but on the new one I am going to try a plenum in a 20H sump and see is say, a mag-float in the plenum would provide good mixing). Alkalinity and Phosphates seem to be issues as well. Alkalinity has been recorded to drop over time with use of a plenum. The buffers that are there to keep the alk high are lost in the plenum system. I use a calcium reactor anyways, and this keeps the alk under control. The phos, as well as organic content of the water is also taken care of by the fuge I also run in the system. Funny thing is how well these two methods work together. See, the other problem with a plenum is trace element depletion...as months or even years can go by without a water change the trace elements in the water get stripped away. Now, the calcium is taken care of with the reactor, but the mud takes care of all the other trace elements. The only thing I dose is iodine via the auto-top-off system. The fuge absorbs any nitrates and phosphates that the plenum may give off though, and so the system is complete. I havent changes the water on this system in over a year, now if i go for three without any problems...I know I have a winner! Otherwise, if it does fail, I will try the mud method on a larger scale. Like the large coral farms. I would terminate the plenum and restart the 45 as a mud tank with macro and lots of critters. I like the fuge I currently run, but I wonder how an even larger version would be... http://www.garf.org/news11p2.html#MUD Link to comment
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