Low Alkalinity Due to Cycling?

[Michael's Marine Park]

Hello everyone! I've got a 25 gallon waterbox peninsula that is 37 days old. I have low alkalinity and am trying to understand the root cause before doing any dosing. I'm hoping some people can help me out. Below is the situation. Is this just due to the tank recently completing the cycle? If so, can you explain how? If it is something else, please let me know. My parameters are below and seem fine outside of this.

I have had low alkalinity since I started testing my tank 15 days ago. The 3 readings over the last 15 days have been 6.4, 6.7, and 6.1. I have used both Red Sea's test and my Hannah Checker.

Here is some background on the tank.

• I started my nitrogen cycle 37 days ago using dry rock, live sand, and Dr. Tim's fishless cycle paired with Nitroturbo and daily dosing of Microbacter7.
• I added a cleanup crew consisting of 3 turbo snails, some other snails, and hermit crabs
• I "completed" the nitrogen cycle by day 25 and added a purple fire fish then
• Around day 30 I added a hammer coral, birds nest, an acan lord, and some zoas. I also added a small amount of live rock from my mature tank at this stage.
• I am not doing any dosing other than daily Microbacter7
• I am doing weekly 20% water changes using RODI water and Instant Ocean salt
• These tests are right before the 20% water change

The parameters

Readings​
Day	37	32	22
Date	5/10/2024	5/5/2024​	4/25/2024​
Time	16:05	17:44	17:40
Temperature	78.8	78.8	78.1
Salinity	1.026	1.026	1.026
Ammonia	0.0	0.0	0.2
Nitrite	0.0	0.0	0.0
Nitrate	16.8	23.3	28.9
pH	8.0	8.2	8.0
Calcium	420.0	400.0	350.0
Magnesium	1,200.0	1,240.0	1,120.0
Alkalinity	6.1	6.7	6.4
Phosphate	0.08	0.00	0.00

 

[Joe31415]

Test the fresh (unused) saltwater. I don't think your alk is 'low' in the sense that something's consuming it, it looks like it was never high enough to begin with.

 

[Joe31415]

Also, if you switch from regular Instant Ocean to Instant Ocean Reef Crystals, that'll bring it up as it runs very high (like 13?). But, I'd start by checking what you have first.

 

[Reefering1]

Those alk numbers look very natural. If you want to be concerned with something, I would start with the po4 zeros

 

[Garf]

Hello everyone! I've got a 25 gallon waterbox peninsula that is 37 days old. I have low alkalinity and am trying to understand the root cause before doing any dosing. I'm hoping some people can help me out. Below is the situation. Is this just due to the tank recently completing the cycle? If so, can you explain how? If it is something else, please let me know. My parameters are below and seem fine outside of this.

I have had low alkalinity since I started testing my tank 15 days ago. The 3 readings over the last 15 days have been 6.4, 6.7, and 6.1. I have used both Red Sea's test and my Hannah Checker.

Here is some background on the tank.

• I started my nitrogen cycle 37 days ago using dry rock, live sand, and Dr. Tim's fishless cycle paired with Nitroturbo and daily dosing of Microbacter7.
• I added a cleanup crew consisting of 3 turbo snails, some other snails, and hermit crabs
• I "completed" the nitrogen cycle by day 25 and added a purple fire fish then
• Around day 30 I added a hammer coral, birds nest, an acan lord, and some zoas. I also added a small amount of live rock from my mature tank at this stage.
• I am not doing any dosing other than daily Microbacter7
• I am doing weekly 20% water changes using RODI water and Instant Ocean salt
• These tests are right before the 20% water change

The parameters

Readings​
Day	37	32	22
Date	5/10/2024	5/5/2024​	4/25/2024​
Time	16:05	17:44	17:40
Temperature	78.8	78.8	78.1
Salinity	1.026	1.026	1.026
Ammonia	0.0	0.0	0.2
Nitrite	0.0	0.0	0.0
Nitrate	16.8	23.3	28.9
pH	8.0	8.2	8.0
Calcium	420.0	400.0	350.0
Magnesium	1,200.0	1,240.0	1,120.0
Alkalinity	6.1	6.7	6.4
Phosphate	0.08	0.00	0.00

The first test would be to confirm your salinity is correct, there's a link to Randy's DIY calibration solutions in my sig if required. What is your salt supposed to mix up at, with regard to Alk? What does freshly made water Alk test at?

 

[Michael's Marine Park]

Test the fresh (unused) saltwater. I don't think your alk is 'low' in the sense that something's consuming it, it looks like it was never high enough to begin with.

I just tested it. At 1.026 salinity and alk of 8.9. Maybe it wasn’t high early on? But I’d think with the water changes I do, I’d bring it up a little at least.

 

[Michael's Marine Park]

The first test would be to confirm your salinity is correct, there's a link to Randy's DIY calibration solutions in my sig if required. What is your salt supposed to mix up at, with regard to Alk? What does freshly made water Alk test at?

Thanks. Freshly made salt at 1.026 salinity has an all of 8.9 when I test it, but the reef crystals Im using should be 13

 

[Michael's Marine Park]

Also, if you switch from regular Instant Ocean to Instant Ocean Reef Crystals, that'll bring it up as it runs very high (like 13?). But, I'd start by checking what you have first.

Thanks. I just checked and am using the reed crystals. Good to know there’s differences in types though.

 

[Garf]

I also added a small amount of live rock from my mature tank at this stage.

What's that tanks salinity and Alk?

 

[Randy Holmes-Farley Verified Community Expert]

The conversion of ammonia to nitrate depletes alk.

 

[Michael's Marine Park]

What's that tanks salinity and Alk?

7.4 Alk and 1.026 salinity

 

[Michael's Marine Park]

The conversion of ammonia to nitrate depletes alk.

Thank you. Does this happen at such a rapid pace that running any reef tank essentially requires some sort of dosing?

 

[TheReefPA]

Recently cycled with IO mix and ran into the same issue. Tank’s alk was running 6.0-6.5 with my IO testing at 8.0. Fortunately still fish only and haven’t transferred over my previous tank’s coral. Trying some left over reef code B to bring up the Alk.

 

[Randy Holmes-Farley Verified Community Expert]

Thank you. Does this happen at such a rapid pace that running any reef tank essentially requires some sort of dosing?

It is not a rate thing, but what effect there is on nitrate concentration because consumption of that nitrate adds back the alk. A 50 ppm rise in alk depletes 2.3 dKH of alk. A drop of 50 ppm adds 2.3 dKH.