Huge drop in Nitrates very quickly?

[jordanrb]

My tank has been running steadily in the low 30ppm for nitrates since the day it was cycled. Weekly water changes never changed it. Tested last night and got 32ppm.

Today I picked up a small chunk of live rock from my lfs to add to an area, about half a pound. Used reef casa rock lock. Added a new crab and that's it.

Did my tests right after as I do anytime I add anything. All parameters are the same that they have been except my nitrates dropped by over half to 12ppm. I was shocked so tried again and got 12.2ppm. Using hanna tester.

Is it possible adding a small chunk of live rock can make this much of a sudden change and only in Nitrates and nothing else? Is it possible the rock putty is having a reaction to the Nitrates?

I know 30ppm is considered on the high end however it has been steady there. I am concerned this drastic of a change will not create issues.

Also noticing my skimmer isn't working as usual after shutting everything down while doing the rock work.

 

[unchainedcoot]

How long has your tank been cycled? I ask because if it’s recent, it’s possible you still had nitrites in the system and those are notorious for giving false high nitrate readings with the hanna

 

[MikeReefs]

The added colonized bacteria on the live rock could have consumed it. But that’s a lot of consumed nutrients for one rock

 

[jordanrb]

How long has your tank been cycled? I ask because if it’s recent, it’s possible you still had nitrites in the system and those are notorious for giving false high nitrate readings with the hanna

Since early December. I got my stuff tested at my lfs as well early January and it all ready fairly similar to my readings.

If it was showing flase readings why would it randomly switch overnight basically?

 

[jordanrb]

The added colonized bacteria on the live rock could have consumed it. But that’s a lot of consumed nutrients for one rock

And it is a tiny rock piece too. I was expecting a few things to change slightly as it is live rock. Everything is almost exactly the same except magnesium dropped around 40-50ppm using my salifert test kit

 

[Fish Fan]

Adding a 1/2 pound chunk of rock did not result in an immediate drop in nitrate. Such a small rock isn't large enough to create an anoxic zone deep in its interior, which is the environment required for denitrifying bacteria to thrive and make any difference lowering nitrate, if that's even achievable in a reef tank.

 

[jordanrb]

Adding a 1/2 pound chunk of rock did not result in an immediate drop in nitrate. Such a small rock isn't large enough to create an anoxic zone deep in its interior, which is the environment required for denitrifying bacteria to thrive and make any difference lowering nitrate, if that's even achievable in a reef tank.

Could the rock lock of had a reaction to the nitrates? I have no idea what could cause it to drop almost 20ppm that quickly when nothing has changed except the rock

 

[Fish Fan]

Could the rock lock of had a reaction to the nitrates? I have no idea what could cause it to drop almost 20ppm that quickly when nothing has changed except the rock

I don't think so. I personally think this may be testing error, but give Randy some time, I'm sure he'll have some ideas to help you.

 

[Randy Holmes-Farley]

Assuming it is not a testing error, I expect the explanation is nitrite as noted above.

Only a small amount of nitrite can read as a huge amount of nitrate. Sometimes 100x. If the rock had nitrite consuming bacteria, then perhaps a small drop in nitrite explains it.

There’s no chemical reaction between nitrate and any reef rocks.

 

[Fish Fan]

There’s no chemical reaction between nitrate and any ref rocks.

Could I please ask; is this because the low to no oxygen zone necessary for denitrification is not possible in at least a typical reef tank? I thought I remembered @Miami Reef explaining why, and it made sense, but the explanation eludes me now

Thank you in advance!!

 

[Randy Holmes-Farley]

Well, what I meant was that there is no reaction with the rock, as there is, for example, with phosphate.

There can be denitrification by bacteria, but that process is slow. A single rock is not going to have any sort of rapid drop in nitrate.

 

[jordanrb]

Assuming it is not a testing error, I expect the explanation is nitrite as noted above.

Only a small amount of nitrite can read as a huge amount of nitrate. Sometimes 100x. If the rock had nitrite consuming bacteria, then perhaps a small drop in nitrite explains it.

There’s no chemical reaction between nitrate and any reef rocks.

Ok thank you for that.

Could this be causing harm to the system if there is Nitrite? I'm assuming if this is the case once the Nitrite is done my Nitrates will spike even higher now?

 

[Fish Fan]

Well, what I meant was that there is no reaction with the rock, as there is, for example, with phosphate.

There can be denitrification by bacteria, but that process is slow. A single rock is not going to have any sort of rapid drop in nitrate.

Just to follow up, you do believe that an anoxic zone for denitrification is possible in reef tanks, if the rock is large enough? So my Remote Deep Sand Bed of many years ago wasn't an entirely dumb idea

Thank you, Randy!

 

[Randy Holmes-Farley]

Ok thank you for that.

Could this be causing harm to the system if there is Nitrite? I'm assuming if this is the case once the Nitrite is done my Nitrates will spike even higher now?

No. Nitrite is not toxic in a reef tank at any level you will ever encounter, unlike freshwater systems.

If 0.3 ppm nitrite might falsely read as 30 ppm nitrate, then converting it to actual nitrate is not going to spike the real nitrate. :)

Nitrate may rise, but I would not be concerned that a "spike" is coming.

 

[Randy Holmes-Farley]

Just to follow up, you do believe that an anoxic zone for denitrification is possible in reef tanks, if the rock is large enough? So my Remote Deep Sand Bed of many years ago wasn't an entirely dumb idea

Thank you, Randy!

Possible? Yes. Likely a large factor in most tanks, especially those not dosing organic carbon? No.

It may have been useful, or not. lol

I've never seen good evidence that adding such a sand bed dropped nitrate by large amounts. Back in the day there was always a lot of discussion about how much animal life was mixing it around, and how deep it had to be, and that certainly may play a role. But it was often stated as a reason folks did not see an effect.

i had one and removed it because I did not think it did anything substantial, good or bad.

 

[Fish Fan]

Possible? Yes. Likely a large factor in most tanks, especially those not dosing organic carbon? No.

It may have been useful, or not. lol

I've never seen good evidence that adding such a sand bed dropped nitrate by large amounts. Back in the day there was always a lot of discussion about how much animal life was mixing it around, and how deep it had to be, and that certainly may play a role. But it was often stated as a reason folks did not see an effect.

i had one and removed it because I did not think it did anything substantial, good or bad.

Yeah I don't think my RDSB attempt - which was in one of those wrapping paper containers; very tall - did much more than make a mess

Thanks again for your help!

 

[jordanrb]

No. Nitrite is not toxic in a reef tank at any level you will ever encounter, unlike freshwater systems.

If 0.3 ppm nitrite might falsely read as 30 ppm nitrate, then converting it to actual nitrate is not going to spike the real nitrate. :)

Nitrate may rise, but I would not be concerned that a "spike" is coming.

Ok thank you.

If I test for Nitrite when I get home and it is at 0 would this be a different issue at that point?

I noticed this morning the water column is full of tiny white particles floating around and my skimmer is making very fine bubbles instead of the larger bubbles normally. Could this have anything to do with it?

 

[Randy Holmes-Farley]

Ok thank you.

If I test for Nitrite when I get home and it is at 0 would this be a different issue at that point?

I noticed this morning the water column is full of tiny white particles floating around and my skimmer is making very fine bubbles instead of the larger bubbles normally. Could this have anything to do with it?

I’m not sure what it would tell you about what may have happened in the past, and I would not bother since in general it’s not useful except if one is worried about whether nitrate results are real. Right now, the nitrate value is fine so there’s no concern about it.

If you did have a bacterial bloom, that can lower N and P. Suspended detritus is not informative of anything.

 

[jordanrb]

I’m not sure what it would tell you about what may have happened in the past, and I would not bother since in general it’s not useful except if one is worried about whether nitrate results are real. Right now, the nitrate value is fine so there’s no concern about it.

If you did have a bacterial bloom, that can lower N and P. Suspended detritus is not informative of anything.

So I tested everything. Nitrates are back to 30ppm as usual. Phosphates dropped to .01. Everything else is normal.

 

[Randy Holmes-Farley]

That’s getting concerningly low on phosphate, if accurate. I’d feed more or dose P.