Alk levels

[unclepregs]

So when I first filled my tank 2 months ago I tested my alk with a Hanna checker and it was 6. Figured I could bring it over to around 8 through 5 gallon water changes over time when the water tests at 8 with my salt. Changed water 3 times since and it is now at 5.6. Very confused as I have 3 frags of softies in the tank and that’s it. Does the 5 gallon changes not help it at all? Thoughts?

 

[The_Paradox]

So when I first filled my tank 2 months ago I tested my alk with a Hanna checker and it was 6. Figured I could bring it over to around 8 through 5 gallon water changes over time when the water tests at 8 with my salt. Changed water 3 times since and it is now at 5.6. Very confused as I have 3 frags of softies in the tank and that’s it. Does the 5 gallon changes not help it at all? Thoughts?

You can never get to the starting number of your fresh salt water with water changes if your starting number is lower than it is. If anything is consuming it you cannot even maintain without dosing.

 

[EricR]

As a fellow user of Hanna Alkalinity dKH Checker (((color-blind here so there's that))), I'll just spew the following thoughts:
-- Reagent tends to sometimes be an issue so at least check against another test or get some new reagent (some have better long-term success refrigerating the Hanna alk reagent)
-- You can easily calculate expected alkalinity increase for water change based on new water alkalinity and volume of water change ... if your new water mix tests lower than expected based on whatever salt you're using, that would be a red flag for possible test error

...oh yeah, be confident in your salinity measurement first

 

[unclepregs]

You can never get to the starting number of your fresh salt water with water changes if your starting number is lower than it is. If anything is consuming it you cannot even maintain without dosing.

My tank is only a couple months old nothing would be using the alk at all. I figured i could raise it through water changes. New 5 gallon mixes at 8 and I’ve confirmed this with testing. You’re saying if my tank is testing lower than my freshly mixed saltwater I’ll never be able to raise it?

I don’t want to have a sps dominated tank and figured i could maintain parameters through weekly water changes since it’s 40g tank. Really only about 31 gallons after rock and equipment.

 

[unclepregs]

As a fellow user of Hanna Alkalinity dKH Checker (((color-blind here so there's that))), I'll just spew the following thoughts:
-- Reagent tends to sometimes be an issue so at least check against another test or get some new reagent (some have better long-term success refrigerating the Hanna alk reagent)
-- You can easily calculate expected alkalinity increase for water change based on new water alkalinity and volume of water change ... if your new water mix tests lower than expected based on whatever salt you're using, that would be a red flag for possible test error

...oh yeah, be confident in your salinity measurement first

Salinity was measured and it’s 1.026. Reagent is still in date and it’s measuring correctly on my newly mixed water. Just wondering if 5 gallon water changes will help raise it. Tank is only 31 total gallons after rock and equipment.

 

[Mr. Roboto]

So when I first filled my tank 2 months ago I tested my alk with a Hanna checker and it was 6. Figured I could bring it over to around 8 through 5 gallon water changes over time when the water tests at 8 with my salt. Changed water 3 times since and it is now at 5.6. Very confused as I have 3 frags of softies in the tank and that’s it. Does the 5 gallon changes not help it at all? Thoughts?

The math checks out. You will just need to do about 30 more 5 gallon water changes to raise it to 8

 

[The_Paradox]

The math checks out. You will just need to do about 30 more 5 gallon water changes to raise it to 8

. You’re saying if my tank is testing lower than my freshly mixed saltwater I’ll never be able to raise it?

You can raise it just not to over 8. The highest it would ever be would be 7. repeating 9 even with 30 water changes. You probably have coralline which devours alkalinity and calcium. The fact it was 6 and after three water changes it’s lower illustrates something is consuming it. Your options are more/larger water changes or dose.

 

[EricR]

FWIW, I like this site as a quick way to calculate expected alkalinity change via water change:

Water Change Chemistry Calculator

P.S. Baking soda (Sodium Bicarbonate) is one way to raise alkalinity in your new water change water, if you're confident with your salinity/alkalinity measurements and decide to go that route

 

[Randy Holmes-Farley Verified Community Expert]

My tank is only a couple months old nothing would be using the alk at all. I figured i could raise it through water changes. New 5 gallon mixes at 8 and I’ve confirmed this with testing. You’re saying if my tank is testing lower than my freshly mixed saltwater I’ll never be able to raise it?

I don’t want to have a sps dominated tank and figured i could maintain parameters through weekly water changes since it’s 40g tank. Really only about 31 gallons after rock and equipment.

That is a misconception. Alk depletes from the first day of cycling in a reef tank.

Rising nitrate and abiotic precipitation of calcium carbonate both deplete alk, and both happens in the early days of a reef tank.

As noted, water changes cannot ever get you to the salt mix alk level if there is any depletion. It’s a mathematical impossibility.