MGilchrist Posted November 20, 2003 Report Share Posted November 20, 2003 Been looking at plans for a DIY denitrator and while it seems like a good idea all the info I have seen seems to refer to marine/reef tanks, so I have 2 questions. 1. can they be used on a freshwater tank and is it worthwhile (reducing requirement for water changes, improving water quality, etc)? 2. Has anyone made one and how did it go (fresh or marine)? Quote Link to comment Share on other sites More sharing options...
Ira Posted November 20, 2003 Report Share Posted November 20, 2003 They can be used in freshwater, but you're better off just doing more and larger water changes or adding some plants. Quote Link to comment Share on other sites More sharing options...
MGilchrist Posted November 20, 2003 Author Report Share Posted November 20, 2003 Ta Ira, so not much point in freshwater. How about marine (still dreaming ) does it help keep water good to point of reducing water changes when coupled with a skimmer, as I imagine water changes are a pain with marine tanks. Quote Link to comment Share on other sites More sharing options...
Ira Posted November 20, 2003 Report Share Posted November 20, 2003 I think with a marine you're better off with a deep sand bed, but if that's not practical and you've already got a good skimmer and everything and still too much nitrate. Then it might be worth it. Quote Link to comment Share on other sites More sharing options...
Warren Posted November 20, 2003 Report Share Posted November 20, 2003 I setup a denitrator on my freshwater tank many years ago. It did reduce the nitrate to some degree but wasn't as effective as I'd hoped. They are quite tricky to setup. You need a large surface area of media in a semi-sealed box. The water has to pass through slowly enough so anaerobic areas are formed but not so slowly that the water goes bad. If too much media is in the water path efficiency is lost. Too little and no anaerobic area forms. Since media is expensive it pays to spend the time getting it right. I used Siporax and purchase 20L of the pond stuff from Jansen’s. It was housed in a glass tank above the aquarium and connected to the main filter system. A very small flow was diverted to the denitrator with a tap to control the flow. Over a 12 month period I experimented with different flow rates to see where it was most effective. It takes about 6 weeks to show the effect of a flow change. With a denitrator running at good efficiency its possible to keep the nitrates in freshwater between 15-30ppm. I eventually gave up on the denitrator idea and focussed on what was causing the nitrates. I found the tank was regularly getting to 100ppm nitrate. After a water change it would drop to about 25ppm (75% water change). 3-4 days later, back up at 100ppm. Eventually I tracked it down to a very high organic load in my tapwater. I went and purchased a RO unit to purify my tap water. Have been using RO water now for over 6 years. It requires conditioning before adding to the tank but now my nitrates measure <10ppm (the plants probably help a lot too). Denitrators are probably best left to marine tanks where a live plenum can be created. Quote Link to comment Share on other sites More sharing options...
MGilchrist Posted November 22, 2003 Author Report Share Posted November 22, 2003 Thanks Warren, much good info. It will be something to look at when, one day, I get a marine tank. But from what you have told me it will be low on the list. Thanks again, Ira too Mark Quote Link to comment Share on other sites More sharing options...
Pies Posted January 13, 2004 Report Share Posted January 13, 2004 Just something to note about Nitrate and water changes: If you have 100ppm nitrate and you want to reduce this to 1.5ppm it will take 16 25% water changes to accomplish this. Or 6 50% water changes. This assumes that no Nitrate is being re-introduced by the water change and that no more nitrate increase during the period between water changes. The math is published. Warrens comments are correct in that getting to the source of the Nitrates is important and avoid introducing them. Marine tanks & nitrate. The plenum 'technology' has been abanded for a DSB (Deep Sand Bed), similar principal without the plenum plate. The plenum needs to be so big (large surface area) that its impractical for most systems. Doesn't mean you can't have one, it just won't do anything benificial. You can now buy/build liquidosed nitrate filters that use a biologically active media that is slowly depleted as nitrates are reduced. Reef runs one on his tank, I also have a friend that runs one on a marine tank in Invercargil. They don't work in freshwater. Nitrate is more of a problem in reef tanks and reducing it to 0 is important for sensile invertibrate health and growth. I run a high load, heavly planted freshwater tank, and my nitrates also creep up. Using RO/DI water systems is probably the best. I have measured my tap water and its about 30ppm Nitrate, which doesn't help. I do big water changes often, run lots of biological filteration and hope for the best now though Pies Quote Link to comment Share on other sites More sharing options...
lduncan Posted January 13, 2004 Report Share Posted January 13, 2004 I know this issue is highly debated, but personally I wouldn't go near a DSB in a marine tank. I don't like the idea of all that crap accumulating at the bottom of the tank. Leave it to the live rock, has worked for me so far, my nitrates are always less than 2ppm, usually 0ppm (measured with both salifert and hagen kits). I don't even do water changes as often as I should, and they don't appear to accumulate. Layton Quote Link to comment Share on other sites More sharing options...
Pies Posted January 13, 2004 Report Share Posted January 13, 2004 I run a DSB in my sump. Nitrates are 0. Quote Link to comment Share on other sites More sharing options...
Joze Posted January 13, 2004 Report Share Posted January 13, 2004 I want something that will go poof no phosphates no nitrates, have an ongoing problem with a tank, cant plant it cant mess with it too much, tried constant water changes even tried a water change with change /lack of food thank god the pool vacuum hose can reach the tank, (hmm wonder if I can use the vaccy scrubber in the tank). If I had the know-how and the dineros I would build an indoor bog garden, come to think of it a kidney pond in a frame would be pretty cool. ok quick brain flit, bog garden/pond upstairs (more natural light for a start) syphoning into tank rather than out Quote Link to comment Share on other sites More sharing options...
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