No Coral but losing Alk fast??

[rweeks42]

Hi. I am about 4months into starting a new LPS tank.I have not put any corals in yet because I’m waiting for more coraline algae. Everything has been consistent; salinity, magnesium, calcium, nitrates, and phosphates are holding great measurements. I will be switching salt soon.
My only problem is alkalinity keeps dropping. I use Red Sea Coral Pro salt. I do a 20% weekly. Before my water change alk is 9.3-9.6. After I go back up to 10.2 Then 2 days later I’m back to 9.6. Where is my Alk going? No corals are using it.

 

[andrewey]

When you say you are waiting for more coraline algae, that means you have some now? Coraline algae growth uses up alkalinity.

 

[rweeks42]

I have just a few small spots less then 1 square inch on 30lbs of dry rock in a 40 gallon tank.

 

[andrewey]

Any other encrusting algae growth you've noticed? Not all coraline algae is purple, so I just want to make sure you're not overlooking the other versions which may be using up your alk.

What about calcifying organism- noticed any proliferation of feather dusters, tube worms, etc.?

 

[lpsouth1978]

Any crabs, snails, shrimp? My initial thought is that your coraline is using it up. I would be willing to bet that the little spots you can see are not all there is. I have found coraline growing in the spots where the rocks touch, or on the bottom of rocks under sand. This is usually a bright pink color though.

 

[rweeks42]

Any other encrusting algae growth you've noticed? Not all coraline algae is purple, so I just want to make sure you're not overlooking the other versions which may be using up your alk.

What about calcifying organism- noticed any proliferation of feather dusters, tube worms, etc.?

Nothing encrusting. I am recently finishing up with my early stage diatom bloom but that’s all going away. I have not noticed any unwanted organisms or pests. I approached this tank with a a very sterile attack plan. I know that doesn’t mean it’s 100% perfect but so far so good.

 

[rweeks42]

Any crabs, snails, shrimp? My initial thought is that your coraline is using it up. I would be willing to bet that the little spots you can see are not all there is. I have found coraline growing in the spots where the rocks touch, or on the bottom of rocks under sand. This is usually a bright pink color though.

Yes I have 6 snails with a little coraline algae and one emerald crab. The dry rock has plenty of surface area so there definitely could be some more growth. I am going to switch to a salt with a 9-10 Alk to help avoid fluctuations. I just don’t want to start 2 part dosing with no coral and a consistent 450 calcium.

 

[Randy Holmes-Farley Verified Community Expert]

Just to clarify the title, you are not losing alk "fast". Assuming your value is accurate, it is only 0.3 to 0.5 dKH per day. That's on the low end, especially at the high alk you are trying to maintain (higher alk means higher daily demand).
Lots of things consume calcium and alkalinity (you wont' readily detect the calcium drop (2-3 ppm per day) that matches that alk drop), including abiotic precipitation on heaters and pumps and bare rock.

Rising nitratealso depeltes alkalinity.

 

[rweeks42]

Just to clarify the title, you are not losing alk "fast". Assuming your value is accurate, it is only 0.3 to 0.5 dKH per day. That's on the low end, especially at the high alk you are trying to maintain (higher alk means higher daily demand).
Lots of things consume calcium and alkalinity (you wont' readily detect the calcium drop (2-3 ppm per day) that matches that alk drop), including abiotic precipitation on heaters and pumps and bare rock.

Rising nitratealso depeltes alkalinity.

Thanks for the feedback. I also just noticed today that my coraline has doubled in size in just a couple days. I think I am going to do small water changes over the next month and find a salt with lower Alk levels. I may end up doing two part dosing to hold the same levels.

Appreciate the feedback from everyone!

 

[andrewey]

You may also look into kalk dosing if you want to maintain your coraline growth rates without too much work. 2 part dosing will also work well.