Organic carbon dosing?

[Clay]

Well, keep in mind this isn't me looking for a solution. This isn't a problem I have, but rather I am curious what happens when organic carbon is introduced to a freshwater tank with high nitrates. My intent was to get a discussion like this going. I didn't seriously think this was a revolution to avoid water changes. That was more of a statement to inspire thought.

With enough aeration, I think we can negate the low O2 levels. Typically, ozone is added in a SW environment to counter the lower dissolved O2 levels, but there are not typically additional aeration methods. We have the option of adding an airstone or increasing surface agitation (something reefers avoid like the plague).

Maybe I'll set up a tank just for this experiment, but there have to be people with HIGH nitrates who wouldn't mind experimenting a little. Who's got high nitrates and a test kit? LETS GO. WTB volunteers!

 

[Just Toby]

I run a fresh water Ray tank and the nitrates can go from 0 to 50 ppm in 1 to 2 weeks despite weekly 25% water changes plus 2 automatic 30 gal changes. My tap water does not register for nitrate.

Over the last 6 weeks I have added a deltec nitrate reactor which is fed with a vodka / ro mix twice per day on a timed peristaltic dosing pump (4ml twice per day with 25% vodka and 75 ro mix)

It is hard to keep the flow rate constant through the reactor and I measure with a redox probe to try and maintain -170mv at this point I get zero nitrate drips flowing from the reactor. At the moment it is not stable enough to run a high enough flow rate to counter the high nitrate production but the theory works and the manufacturers say that 3 months could be the full maturity time.


I also periodically run an ion exchange resin filter on the tank (every week or so)

The rays consume a lot of food and I think other Ray keepers do not keep on their nitrates enough, I want to maintain less than 10-20 ppm.

 

[Danger_Chicken]

With enough aeration, I think we can negate the low O2 levels. Typically, ozone is added in a SW environment to counter the lower dissolved O2 levels, but there are not typically additional aeration methods. We have the option of adding an airstone or increasing surface agitation (something reefers avoid like the plague).

I believe O3 is added to clean the water not oxygenate it. It oxidizes the DOC's which cause yellowing of the water. I know reefers hate bubbles but I think surface agitation is still common, but that's just a guess from what I remember from seeing display tanks at the lfs. O3 is unstable so it may deteriate to O2 giving oxigenation as a side effect but that's speculation on my part.

Over the last 6 weeks I have added a deltec nitrate reactor which is fed with a vodka / ro mix twice per day on a timed peristaltic dosing pump (4ml twice per day with 25% vodka and 75 ro mix)

It is hard to keep the flow rate constant through the reactor and I measure with a redox probe to try and maintain -170mv at this point I get zero nitrate drips flowing from the reactor. At the moment it is not stable enough to run a high enough flow rate to counter the high nitrate production but the theory works and the manufacturers say that 3 months could be the full maturity time.

I'm not famliar with that denitrator, but I know from using the sulfur type that the flow rate was just a couple drips a second. Even at the rate it will consume more nitrate than the tank can produce. It will just take some time to bring it down. Mine took a week to seed and then the effluent went to 0 nitrate, sounds like you're already there. Changing the tank water to further reduce the nitrates should speed up the process. Please keep me posted.

I dont think a "water change free" tank is possible

I've read a few accounts of reefers claiming to have achived this (several years w/o water change). They tend to run their tanks as entire eco systems. I don't think it's currently possible on a FW monster tank, but think it could be done on a smaller planted tank. It's my goal to create something like the reefers have with a well rounded eco system that helps sustain the tank environment.

 

[Clay]

Interesting input Toby. I'd like to see how it works for you on a longer term basis.

Danger_Chicken, you're probably right. I'll read up about ozone usage with carbon dosing and see if I can get more information.

 

[Just Toby]

In the last day the redox has dropped below -250 mv which produces sulphur dioxide (smell of eggs) I am upping the drip rate but you have to be careful not to crash the bacteria, I am bringing it back to normal slowly.


You can rig up the redox control to open an extra solenoid feed of water but this can cause some instability or "hammering" so I am keen to not use this route.

 

[Just Toby]

Interesting input Toby. I'd like to see how it works for you on a longer term basis.

Danger_Chicken, you're probably right. I'll read up about ozone usage with carbon dosing and see if I can get more information.

Have a look at the d and d (deltec uk) site as they have a good article and they have an alternative product but it looks to be based on marine only as you need a skimmer to removevthe waste.

 

[Clay]

Just Toby, do you have any updates on your vodka usage?

 

[Sik.10a]

Jus set up an aquamedic nitrate reductor. Jus began to cycle it yesterday, it's a new tank toy to me, Can't wait to see some results,,,,,,.... My mate has this one and his works. My wc schedule will not change- about 50% once or twice weekly- I can't get my nitrates below 40ppm, hopefully this soles my prob, can connect in a couple of weeks- gotta let bacteria build up first