Finding source of high Alk

[InvaderJim]

Recently I've gotten better about testing the ALK in my tank, and test it about the same time every night. It's come to my attention that my ALK hovers around 9.6-9.8. My tank is still fairly new, around the 5 month mark so it isn't really consuming anything. However I'm a little confused as to why my ALK is actually that high. I use NeoMarine salt and have tested the alk in a fresh batch and it's nowhere near those levels, I've also tested the tank after a water change and it hardly budges. The only thing I'm dosing is trisodium phosphate. Could the trisodium phosphate be contributing to my high ALK levels or is it something else?

 

[MnFish1]

1. Why are you dosing trisodium phosphate?
2. What else is in your tank? (i.e. coral/fish)
3. Are you sure your test is correct?
4. Alkalinity can vary through the day - could it be you're testing it at a 'peak time'?
5. Do you use tap water or RODI?
6. Some chemical reactions with nitrate, etc can do it.

Do you think its causing a problem?

 

[InvaderJim]

1. I'm dosing it to raise the phosphate levels in the tank because they were previously undetectable.
2. 6 fish, and corals.
3. I've tested using the Hanna checker and two different regents, one being brand new. I've also cross checked it with Salifert.
4. I've tried testing a few different times, including just now, and it's consistently 9.5+.
5. RO/DI through a 5 stage system
6. I've seen a post from Randy about nitrates lowering can contribute to the ALK rising but I think 7.5 to 9.5 is a bit extreme.

While I don't think it's a problem, especially since the numbers are stable. It's more of the why. I'm trying to understand what could be causing it to avoid future potential problems.

 

[MnFish1]

1. I'm dosing it to raise the phosphate levels in the tank because they were previously undetectable.
2. 6 fish, and corals.
3. I've tested using the Hanna checker and two different regents, one being brand new. I've also cross checked it with Salifert.
4. I've tried testing a few different times, including just now, and it's consistently 9.5+.
5. RO/DI through a 5 stage system
6. I've seen a post from Randy about nitrates lowering can contribute to the ALK rising but I think 7.5 to 9.5 is a bit extreme.

While I don't think it's a problem, especially since the numbers are stable. It's more of the why. I'm trying to understand what could be causing it to avoid future potential problems.

I believe @Randy Holmes-Farley has also mentioned increasing alkalinity from 'rock' as well. I do not see an alkalinity of 9.5 as 'a problem'.

 

[lany2008]

if your rocks are human made, it may generate ALK, depend on the materials.

 

[christianscorals]

i would test alk from at least 3 fresh batches to make sure it’s truly consistent. otherwise alk at that level should not be a problem as long as you can keep it hovering over those numbers