Waterchanged two days ago now RTN event

[javisaman]

Hi All,

I did a 10% waterchange like I usually do a couple of days ago and my corals hadn't really opened up yesterday. Today I checked my tank and of my SPS STN'd about 30%. The parameters right now are:

9.5 Alk (before waterchange was 9.25)
430 Ca
1250 Mg
0.05 phosphate
0 Nitrate

I've already started mixing more saltwater (another brand) to do a large water change today, but I'm not 100% sure if it's the right idea. The new brand I'm using has much lower Alk than the previous and my tank and I feel like that might stress the tank out even more.

Help is greatly appreciated!

 

[javisaman]

Bump. Doing some reading it looks like my alk might be a bit on the high side. Doing a 33% water change with 7.5 alk may not be the end of the world.

 

[AZMSGT]

Zero nitrate is a bigger problem than the alk

 

[720 Reefer]

Zero nitrate is a bigger problem than the alk

Agreed. 9.5 Alk is not a problem at all as long as it's stable (which sounds like it is). Zero nitrate is a definite problem though.

 

[javisaman]

Should I add two part to my salt mix to get the alk closer to the tank then? Should I be adding both alk and cal?

 

[vetteguy53081]

Two thoughts that jump out are:
Was the water temp for new water colder than tank?
Last time you calibrated salinity checker which may be giving false readings?
I also wonder if there are any microscopic protozoans in the water used . These protozoans are a family of single cell microscopic organisms with cilia that are found in the water column

 

[720 Reefer]

Should I add two part to my salt mix to get the alk closer to the tank then? Should I be adding both alk and cal?

I have done that when my new water is reading low and had no issues. But yes definitely add both in equal parts if you do.

 

[javisaman]

I use two methods to test salinity: Milwaukee Digital Refractometer and a standard optical one. The new water temp was 70F, tank stays at 79. The size of the water change was 10% and I used RO/DI + Red Sea Pro. I doubt any protozoans would have entered that way. I've done the same thing for the past year and a half since the tank was up. I'm beginning to think it's not the waterchange, but something else. I've put some polyfilter in the tank to see if there are any contaminants.

Thank you for all of your suggestions!

 

[javisaman]

Hi All,

Just an update. The waterchange and the polyfilter have helped so far. None of the corals have RTN since. Keeping fingers crossed. I think the combination of high alk, 0 nitrates, and high light (LED/T5) is pushing the tank too much. I've decided to turn off the T5 for now and reduce the fuge photoperiod until things improve more.

Thanks again!