Alkalinity struggle zoa only tank

[TampaSmitty]

Alk 7.6
Ph 8.2
Nitrates 9.2
Phos 0.26
Calcium 530
Salinity 1.024
Been mainly struggling with alk. Seems to drop between .02 and .04 per day. I feed reef roids maybe once every 2 weeks at around 5-6 ml. Tank is a 13.5 maybe 11-12 gallons. For some reason I don’t understand why my alk is depleting so fast tank has only 30 heads or so of zoas. I don’t run any chemicals at all. Change the water ever 1-2 weeks at 30-40%. It does not have a sealed lid. Any help would be appreciated. I have had some hair algae on 2 plugs very little in the scheme of things but I am dipping them so that will soon be gone.

 

[Ron Reefman]

So you are not doing any dosing of Ca or alk on a daily basis?

I have a fairly new 40g tank with mostly new frags and I dose 25ml of alk a day and 50ml of Ca. And then I test every week.

 

[TampaSmitty]

So you are not doing any dosing of Ca or alk on a daily basis?

I have a fairly new 40g tank with mostly new frags and I dose 25ml of alk a day and 50ml of Ca. And then I test every week.

I dosed some baking soda a few days ago as alk was at 6.3 and went by water volume but dosed to 8.5 Sunday. And now it’s at 7.6
Surprisingly no zoas were affected. That’s the only time I’ve dosed anything. Newish tank 4-5 months in. Still slight bit of diatoms on there way out.

 

[homer1475]

Any coralline algae growing? That will consume alkalinity.

 

[TampaSmitty]

Any coralline algae growing? That will consume alkalinity.

Hard to say I used caribsea life rock it’s purple.

 

[Ron Reefman]

Hard to say I used caribsea life rock it’s purple.

Coralline algae will start on the glass if you leave it untouched for a week or so. That would confirm you have it growing.

Test your water for Ca, alk & Mg. Don't dose anything or do water changes for a few days. Then test again. Then go to Reef Chemistry Calculator at https://reef.diesyst.com/chemcalc/chemcalc.html. Put in your original levels and your new levels and pick the brands of Ca & alk you want to dose. It will tell you how much to add.

Then take those amounts and divide by the number of days between your first test and the second. That's going to be very close to what you should be dosing every day.
Example: Alk on day1 is 8.0dKH. On day 3 it's 6.5dKH. The calculator says you need to add X amount of alk (like baking soda or soda ash). Let's say it says 30ml of baking soda. Then divide 30ml by 3 days and you find you should be adding 10ml every day.

I test every Monday and every morning I dose 30ml of soda ask for alk and 50ml of Dowflake for Ca. I use soda ash and Dowflake mixed to Randy Holmes-Farly's receipe #1.

 

[Randy Holmes-Farley]

Im confused. 0.02 to 0.04 dKH per day is an incredibly small alk drop that is easily countered with occasional doses of baking soda.

 

[nereefpat]

I agree that's a tiny amount.

Even without stony corals present, alk can drop due to coraline algae or increase in nitrate. Anything around 0.5 dKH per day wouldn't be surprising to me.