Low alk (but good pH) causing fish death?

[Nerdist Aquarist]

Wanted to get some opinions if low alkalinity can cause fish death. As indicated pH is good averaging 8.2 (verified measurement is accurate).

I've recently rebooted my tank and currently going through the ugly hair algae phase now. Started with dry rock and dry sand. It's been about 3 months since tank has completed cycling. I've been slowly adding fish and tangs as the primary way to manage algae growth. However, I've now lost 2 Powder Blue Tangs. First lasted a few days , and the second less than 2 weeks. At first I thought it was just because those fish are notoriously difficult to keep, especially without a quarantined setup. I knew something was seriously wrong when 2 clowns died overnight after looking healthy for 2 weeks.

I tested my Alk it it's around 4.5 dkh, I'm slowly bringing it up now. I didn't consider dosing alkalinity as it's just rocks for now, coral will come much later. I didn't anticipate alk to be this low anyway. All the other parameters like Calcium, mag, nitrate, phosphate are fine.

So my question is can low alkalinity be enough to cause fish death? And again, keep in mind that pH is completely within a good range. I run a UV sterilizer 24/7.

 

[LPS Bum]

Wanted to get some opinions if low alkalinity can cause fish death. As indicated pH is good averaging 8.2 (verified measurement is accurate).

I've recently rebooted my tank and currently going through the ugly hair algae phase now. Started with dry rock and dry sand. It's been about 3 months since tank has completed cycling. I've been slowly adding fish and tangs as the primary way to manage algae growth. However, I've now lost 2 Powder Blue Tangs. First lasted a few days , and the second less than 2 weeks. At first I thought it was just because those fish are notoriously difficult to keep, especially without a quarantined setup. I knew something was seriously wrong when 2 clowns died overnight after looking healthy for 2 weeks.

I tested my Alk it it's around 4.5 dkh, I'm slowly bringing it up now. I didn't consider dosing alkalinity as it's just rocks for now, coral will come much later. I didn't anticipate alk to be this low anyway. All the other parameters like Calcium, mag, nitrate, phosphate are fine.

So my question is can low alkalinity be enough to cause fish death? And again, keep in mind that pH is completely within a good range. I run a UV sterilizer 24/7.

I’ve never seen nor heard of low dKh killing fish.

I’d look to salinity, temp and ammonia first. Obviously diseases like velvet, crypt etc too. Heavy metals like copper in the water can also be a problem. But alkalinity, nitrates and phosphates aren’t typically of any concern for fish.

 

[Reef.]

Not sure why you are so convinced your ph is accurate yet your alk is apparently crazy low, ph is much harder to get an accurate reading.

I agree with LPS Bum, I would be looking for a different cause and also wondering why if my alk is correct, why it’s so low, especially with no corals.

 

[Nerdist Aquarist]

Not sure why you are so convinced your ph is accurate yet your alk is apparently crazy low, ph is much harder to get an accurate reading.

I agree with LPS Bum, I would be looking for a different cause and also wondering why if my alk is correct, why it’s so low, especially with no corals.

I do know biological processes do neutralize some of the buffering capacity, corals are not the only things that reduces alkalinity. I'm not really surprised alk decreased, but what caught me off guard was that it would be that crazy low. I guess new tank syndrome and going through cyano/dino blooms really took a big bite out of it. I haven't done any water change in a few months, not even after the cycle. I'll be doing one soon.

I suppose fish disease is a strong possibility as well.

 

[00W]

I agree with the two above wholeheartedly.
Don't mean to be rude but I don't know what a restart is? Nor have you given tank size . I don't know what "good " means in regards to parameters.
The fact that you haven't changed any water in a long time on a tank that new could be part of it. Poisoning perhaps.
I don't know what filtration you have either.
What top off water are you using?
Check salinity.
Powder blues need pristine water conditions and large tanks.
Any info you care to divulge would be greatly helpful.

 

[Randy Holmes-Farley]

IMO, it would be unusual to have pH that high if alk is that low. I expect one or both of the measurements is incorrect, and I doubt either killed a fish.