Why is my alkalinity so low?

reeflover · Apr 6, 2020

Hi everyone! I am not new to the hobby, but I have been tank-less for the past couple of years while I worked my way through my final years of college. Now that I have graduated and moved into my own place, I have set up a Fluval Evo 13.5! It has been up for a few days now and has about 8 lbs of live rock, about 4 lbs of BRS dry rock, and 15 lbs of live sand.

I was doing some water testing yesterday and was curious about what my alkalinity was…I checked the tank and it was 4.8. I wasn’t too worried, I figured it may have something to do with the cycle and that it would figure itself out eventually. Just to be safe I decided to check a batch of brand new saltwater I had made. That also came out at 4.8. I am so confused as to why. I am using RO water from a brand new BRS RO/DI system, AccuraSea 1 salt, and mixing to 1.026. At that salinity, the salt advertises alkalinity of 8 dKH, yet I am getting 4.8. I am using a brand new Salifert test kit (that is still well within its expiration date) and following the directions to a T.

A little more backstory: I had a small pico reef in my apartment my sophomore year of college that was doing really well, but then I started having alkalinity issues, again. I could not get it above 5-6 and keep it there. Even with water changes. At that point, I was using the LiveAquaria salt and RO/DI water from the grocery store. I didn’t have any stony corals in the tank, just softies and zoas so I was confused as to where it was going? I would dose the tank, slowly raise my alkalinity to 10 or so, then it would be back down to 6 within a couple of days.

I don’t want to run into the same issues as before and have to take this tank down because of it. Has anyone else had this issue?

Thanks in advance!

Copingwithpods · Apr 6, 2020

Sounds like a test kit error. A reagent could have been contaminated or left open.

AltitudeAquarium · Apr 6, 2020

Use the principles of scientific data evaluation. If the results are strange, test again. If the results still do not meet what you expected then test against a known source. What I do is I take the water and my test kit to a LFS. I have them test my aquarium and if they get similar results I can feel comfortable that my testing procedure/kit is okay. If they get something completely different, I use my test kit and test their water if it does not match, I then know I have a bad test kit or method in conducting the test. My two cents.

Randy Holmes-Farley · Apr 6, 2020

Some folks read Salifert syringes backwards. Double check that and ensure that if it took a while syringe of titrant to get to the endpoint, the alkalinity is high, not low.

MTBake · Apr 6, 2020

Make sure what you are using to check salinity is accurate as well. Wondering if a new batch of saltwater also checks low as well.

Rybren · Apr 6, 2020

Are you reading 0.48 remaining in the syringe? If so, then that equates to 8.0 dKH on the Salifert test. With 4.8 dKH, you should have 0.68 remaining in the syringe.

reeflover · Apr 7, 2020

Rybren said:
Are you reading 0.48 remaining in the syringe? If so, then that equates to 8.0 dKH on the Salifert test. With 4.8 dKH, you should have 0.68 remaining in the syringe.

I am reading 0.68 remaining in my syringe.

I suspect at this point what you all are saying-an issue with the kit itself. My closest LFS is 1.5 hours away so I’ll just need to order a second kit to verify. Thanks for the help!