I've been running a successful methanol denitrater for over a decade. Recently had to breakdown and startup my denitrater because we were tenting the house for termites and thought I would update this post on things i've learned.
Methanol -
The product nitragone is about 25% methanol IMO. I use pure methanol (M1 racing fuel) and cut it to 50% with RO water. I've found that >50% will damage the tubing over time. Also, at higher concentrations some of the methanol will evaporate while dosing. Methanol is an organic carbon like vinegar, vodka, nopox...etc The bacteria use organic carbons as a building blocks to make more bacteria. If you have a lot of excess organic matter in your system you may notice you dont have to feed as much methanol.
Bacteria -
Purple Non-sulfur bacteria PNSB is by far the best choice for a denitrater. The product I use is called PNS ProBIO. It can be found at hydrospace.store or algaebarn.com. I've seen similar products sold by BIOSUN.
Water Flow inside the chamber-
More flow is better. I've found a water flow pumps like MP40,MP10, Jebao Rw-15 or similar koralia work best. Place it low enough so it doesnt create an air vortex but gives good circulation. I run a Rw15 in pulse mode at highest speed. I get a little back/forth wave at the top but not much surface tension. If you dont have enough flow the methanol will not mix in the chamber and all the bacteria will just grow on the top water surface.
Egg Crate -
Dont put egg crate in the middle, just line the edges and bottom. (zipties work well) Anything in the middle will just block the flow of water and prevent the methanol from mixing when you dose.
Cycling -
Cycle only as often as needed to control nitrates. Usually, 1-3 times per day is fine. You can delay the methanol dose an hour or 2 after a flush to extend the cycle time. The bacteria will go into a hold/suspend state and wait for the methanol. I currently cycle once a day, dosing 5ml of 50% methanol in a 10gal chamber. This supports a 250gal system with 20 fish. My nitrates hold between 5-10 ppm on a salifert test kit. If you target too low for nitrates you'll upset the ratio of nitrates to phosphates and may end up with algae/cyano bloom.
Sulfur smell-
Bacteria preference = Iron>Nitrates>Sulfates. The Bacteria break the bonds and use it as energy (ie: NO3-->NO2-->NO--N2-gas) If you are getting the sulfur smell at the end of your cycle or while flushing, your bacteria ran out of nitrates and started using sulfates. You need to do one or more of the following: decrease methanol dose, run more cycles per day, delay methanol after chamber flush, or feed the chamber some nitrates to compensate. I use to feed nitrates about 2 hours before end of cycle. My experience the Purple Nonsulfur bacteria doesnt really go after the sulfates.
Phosphates -
IME the denitrater doesnt remove/eatup much in the way of phosphates. I still have to run GFO to control phosphates. Probably the only downside to a denitrater.
Refugium/Chaeto-
IME a denitrater and chaeto/macroalgae type refugium are not really compatible.
Misc-
an interal overflow box inside the chamber helps to keep the "chunky" biomass bacteria from flushing out.
The bacteria that grows on the sides of the chamber and in the egg crate is clear to tan and thick viscosity.
Dosing peroxide in your system will KILL the bacteria in the denitrater.
Try to flush the denitrater above the water line in the sump and near the skimmer.
If you've made it this far you are an amazing person!.
I hope this has been helpful. feel free to email me direct drtpharmd99@aol if you need help starting up or troubleshooting your denitrater.
Dave
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