Nitrates disappeared??

[Waters]

Have a strange one..........I have always kept my nitrates at about 5 in a SPS dominant system. Recently I did some major equipment upgrades which caused me to remove my skimmer, UV, carbon, and GFO for several days. I expected my nutrients to be through the roof (no changes in feeding). I tested nitrates to find out that they were totally nonexistent. How could removing every form of nutrient removal I have cause my nitrates to bottom out?

 

[Randy Holmes-Farley Verified Community Expert]

There are many interlocking methods of nitrate consumption that you likely impacted, and I have no idea which (if any) of these actually caused the result. It could be several of them, or it might even be test error.

But here are some possibilities:

1. Denitrification in low O2 areas MUST have organic matter to consume, and more organic matter may mean more denitrification (hence one reason people dose organic carbon). Removing skimming and GAC (and even GFO) will likely allow organic levels to rise, and hence you may be experiencing more denitrification.

2. Same is also true for growth of aerobic bacteria that consume the organics and inorganic nutrients.

3. The UV stopped killing suspended bacteria, and fewer dead bacteria may mean less release of nutrients from them.

4. Removing these devices would be expected to alter the trace elements in the water substantially, and perhaps they are now more bioavailable and something is growing better, taking up more nutrients.

5. Low phosphate may have been limiting growth of something and removing the GFO may have removed that limitation, so it grows more and nitrate declines (many people see this under the right circumstances).

6. Changing skimming may have altered the tank pH (it can raise or lower or both), and that may impact organism growth and uptake of nutrients.

 

[Waters]

There are many interlocking methods of nitrate consumption that you likely impacted, and I have no idea which (if any) of these actually caused the result. It could be several of them, or it might even be test error.

But here are some possibilities:

1. Denitrification in low O2 areas MUST have organic matter to consume, and more organic matter may mean more denitrification (hence one reason people dose organic carbon). Removing skimming and GAC (and even GFO) will likely allow organic levels to rise, and hence you may be experiencing more denitrification.

2. Same is also true for growth of aerobic bacteria that consume the organics and inorganic nutrients.

3. The UV stopped killing suspended bacteria, and fewer dead bacteria may mean less release of nutrients from them.

4. Removing these devices would be expected to alter the trace elements in the water substantially, and perhaps they are now more bioavailable and something is growing better, taking up more nutrients.

5. Low phosphate may have been limiting growth of something and removing the GFO may have removed that limitation, so it grows more and nitrate declines (many people see this under the right circumstances).

6. Changing skimming may have altered the tank pH (it can raise or lower or both), and that may impact organism growth and uptake of nutrients.

Thanks for the very informative response. I guess all could be a possibility except the altered PH since that was still being monitored. I would probably eliminate testing error since I have always tested using the same method....I also double checked with different test kits because I couldn't believe the original result. I guess it shows you what can happen "behind the scenes" when changing anything in our tanks. Every action has a reaction