Nitrate reduction

[MarkO]

Yeah, unfortunately peoples experiences do not back up a basic dilution theory. I think it has to do with the live rock, sand and other means by which the nitrates become waterborne.
Back in the day it was (about 5 years ago), it was thought that nitrates are broken down in oxygen depleted areas of the tank (hense deep sand bed theory). But at a rate significantly less than the ammonia--> nitrite --> nitrate cycles.
Also back then, I was told to add a macro-algal refugium, which seemed to work for me. It took about a month to get my nitrates from about 30ppm to <1. Prior to the refugium, I noticed a lot of detritus, and also fed my fish quite often. I think vaccuming out the detritus will also help, and cut back on feedings, which shoudln't be an issue here.
Also keep the skimmer going

 

[NateHanson]

from what I've read, like 99% of the bacteria is on surfaces. A good deal of the bacteria in the water is skimmed out too. I dont think water changes will afffect the cycle.

I agree that the bacteria are nearly all on surfaces in the tank, not suspended in the water, but that doesn't mean that water changes can't have an affect on the cycle. By replacing water with "clean" water, you're removing the food source that facilitates the bacterial blooms that we call a cycle. The final step to the cycle is a build-up of nitrates, and then a bloom of bacteria which can utilize the nitrate and turn it into nitrogen. By reducing the nitrates at this point, you may increase the time it takes your tank to build up its own population of denitrifying bacteria.

I'd just sit back, be patient, get a RODI, and let the tank cycle. Maybe do a small water change to keep other nutrients and minerals in balance, but I wouldn't do a big water change at this point.

 

[wrassefan]

I just reread the orig post and at 3 weeks the cycle is prob not finished. I would leave it alone as others have said above for a few more weeks. Once you have achieved zero readings across the board for a week...then you know the cycle is finished. I wouldn't do a water change at this time....it can extend the cycle

 

[zear0]

yeah, i was also thinking 3 weeks is kind of quick for a complete cycle... patience is the name of the game here.

is there any chance your nitrate test kit might be off?
what kind of algae do you have now?

I cycled my tank with 85# of live rock and the nitrates never went above 25. Now they are at 0 and I've only ever done 15-20% RODI water changes. My rock was very cured when I started my tank. I think you said you have 180# of live rock and the nitrate is >160. 160 seems really high, especially after only 3 weeks.

How cured was your rock when you got it?
How cured was your live sand when you got it?

whatever you do, don't use tap water if you do any major water changes. it could cause a major algae bloom in your tank.

 

[JohnK]

160 ppm as a whole lot of nitrate. IMO that's far more than you need to feed developing denitrifying bacteria, It may take quite a long time for that to drop on it's own.

just an opinion.

jk

 

[mitch]

I think the problem was that i was using tap water before, and when i measured the nitrates in the water it was around 40 ppm. I am now using distilled water so the nitrates coming in from the tap i no longer have to worry about.

I'm going to do a 2 50% water changes this weekend.

Thanks for all the help guys.

 

[mitch]

I think the problem was that i was using tap water before, and when i measured the nitrates in the water it was around 40 ppm. I am now using distilled water so the nitrates coming in from the tap i no longer have to worry about.

I'm going to do a 2 50% water changes this weekend.

Thanks for all the help guys.

 

[NateHanson]

So the tank was started with tap water? At 40ppm for starters, I think that explains the problem.

Nate

 

[zear0]

is 40 ppm nitrates in tap water something to be concerned about?

 

[NateHanson]

For who? I certainly wouldn't put it in my tank - definitely buy a RODI. But for human consumption, you'd have to translate it into mg/L. The EPA says anything below 10mg/L is fine.

 

[Matt L.]

Key Pointers for Everyone

Just to clarify, these pointers are directed at everyone, not just the original thread starter. So, from your only official, resident nitrification/denitrification scientist:

1. Your test kit probably isn't accurate. People look to these over-the-counter test kits as if they are the Bible. Nothing could be further from the truth. A variety of test kit shortcomings and user error can lead to wildly inaccurate result. No one should ever take drammatic actions based on what their test kit says. Any reading should be confirmed by at least two other, different brand test kits.

2. Using tap water is not compatible with succesful reefkeeping. Switch to RO/DI water. If you aren't up for a RO/DI filter right now, RO/DI water can be purchesd from your LFS for very little. What did Skiptons use to sell it for? Something like $0.50/gal.

3. Water changes are a succesful way to reduce nitrate. A 50% water change will reduce 50% of your nitrate levels, assuming there is no nitrate in your makeup water. In your case, as your makeup water was full of nitrate, you were basically removing nitrates from your tank, only to add them again. In other words, the water change was a waste of time. Because the majority of the nitrite oxidizing organisms are located on solid surfaces, you may safely change up to 50% at a time. However, you should let a week go by in between 50% water changes, in my experience.

4. Denitrification may or may not happen in your tank. So don't count on it. I personally don't believe in deep sand beds (I use a shallow sand bed), but I also don't tell people not to use them. Its personal choice. Regardless, denitrification, if it is happening in your tank, probably won't be able to keep up with nitrification. A refugium is a much more healthy (IMO) way to export nitrates.

5. Lower your bioload. If you are using RO/DI water, and you still have high nitrates, you are overfeeding or you have too much bioload for your system. Remove fish and or feed less.

Hope this helps everyone who has high nitrates,

Matt

 

[Matt L.]

Better Late than Never

What % of water should i change out to drop the nitrate levels? It has cycled for 3 weeks now and my nitrates are still at 160 ppm +, no ammonia and no nitrites. I don't want to overdue the water change, anyone have an idea how much to change out at any one time, and over how much time? Also will the live rock and sand help keep the nitrate levels at a safe level with normal water changes being done weekly.

Thanks for everyones help.

It is not inconceivable to wind up with 160ppm nitrates if you had a really wicked cycle.

From the scientific point of view, I would actually advise you to do a 50% water change with RO/DI (or distilled) water.

Typically, you don't change your water until after the cycle is complete, as it prolongs the cycle.

However, the presence of such a high level of nitrate, I fear, will inhibit further nitrite oxidation top nitrate, and once nitrite oxidation halts, ammonia oxidation is soon to follow.

In other words, its better to have your cycle complete late than never!

I would also get a completely different brand of test kit and or have an LFS verify that result.

Matt

 

[mitch]

Thanks for everyones help.