Strange ALK issue

[User]

Hi guys

have a 2 year old 180, lightly stocked (working on it). I don’t dose because I don’t have the requirement beyond what 15% WC every 2-3 weeks takes care of.

corals: a couple hammers, 2 torches, a big Duncan, a big GSP, big Xenia, 2 large encrusted favia, two fungia, 3 small cyphastrea.

I have a weird issue with ALK that I can’t get a handle on.

parameters:

salinity: Rock solid at 1.026
pH: 8.02-8.17.
Nitrate: 5-6ppm requires occasional dosing with stump killer
Phosphate: 0.2ppm yesterday, around 0.15-2ppm for past 4 months.

Calcium : 425
Magnesium: 1245

Alkalinity: 13.8

I tested my freshly made salt water (instant ocean) and got 11dKh for the alk.

if I do a water change and test the next day, ALK in tank is around 12.8, will stay like that for 1-2 weeks, then go up to 13.8.

I know I can knock back the alkalinty in the new salt water using acid then heavily aerate to get the pH back up, but I’m stumped with how to drop the ALK in the tank. I’m also confused by the rise in tank after1-2 weeks

Thanks for any advice and info!

 

[ludnix]

There is a great thread with some sage advice and questions from Randy in this thread by someone with a similar issue:

Alkalinity rising?

I'm finally getting to the point where my GHA garden is dying off and I expect it to all be gone shortly. My previous high pH levels are dropping back down - it had been swinging between 8.2 to as much as 8.8 but is now between 8.2 and 8.4 and I think it will be back to the old range of 8 to 8.2...

www.reef2reef.com

 

[Randy Holmes-Farley Verified Community Expert]

Hi guys

have a 2 year old 180, lightly stocked (working on it). I don’t dose because I don’t have the requirement beyond what 15% WC every 2-3 weeks takes care of.

corals: a couple hammers, 2 torches, a big Duncan, a big GSP, big Xenia, 2 large encrusted favia, two fungia, 3 small cyphastrea.

I have a weird issue with ALK that I can’t get a handle on.

parameters:

salinity: Rock solid at 1.026
pH: 8.02-8.17.
Nitrate: 5-6ppm requires occasional dosing with stump killer
Phosphate: 0.2ppm yesterday, around 0.15-2ppm for past 4 months.

Calcium : 425
Magnesium: 1245

Alkalinity: 13.8

I tested my freshly made salt water (instant ocean) and got 11dKh for the alk.

if I do a water change and test the next day, ALK in tank is around 12.8, will stay like that for 1-2 weeks, then go up to 13.8.

I know I can knock back the alkalinty in the new salt water using acid then heavily aerate to get the pH back up, but I’m stumped with how to drop the ALK in the tank. I’m also confused by the rise in tank after1-2 weeks

Thanks for any advice and info!

Dosing nitrate tends to raise alkalinity (2.3 dKH per 50 ppm dosed). I'm not sure if that is the main issue, however.

 

[User]

Dosing nitrate tends to raise alkalinity (2.3 dKH per 50 ppm dosed). I'm not sure if that is the main issue, however.

Yeah, but I only dose 3-4ppm per week to keep it at 5-6ppm.

Ill read that thread that was posted- missed that in my search
Thanks

 

[User]

First page of that thread... I have 60lbs of BRS reef saver and 50lbs pukani in the tank... and I joined several pieces of the RS with hydraulic cement. The Pukani was in a vat of saltwater for 5 months with regular water changes and I only put it in The tank when phosphate was reading zero between changes.
The Reefsaver rock leaching Alk is a new one to me.

guess that’ll be it then?

 

[User]

At the time I bought the BRS reef saver, I spoke with Randy who told me it was mined from an inland quarry in Florida, and is NOT a cement based fully artificial rock similar to Marco rock. I remember going over that point with him several times. And when it arrived, it had shell and worm tubes embedded so assumed it was accurate.
So, I’m doubting that the rock is to blame.

theres 120lb of Caribsea Sea-flor special and 40lbs of Fiji pink aragonite in there.Aragonite sand appeared to be a shared characteristic of tanks in that referenced thread.

 

[Randy Holmes-Farley Verified Community Expert]

Yeah, but I only dose 3-4ppm per week to keep it at 5-6ppm.

Ill read that thread that was posted- missed that in my search
Thanks

I'm not claiming that its the issue, but it will build week to week unless something is using the alk.

The best bet in such a situation is, IMO, to do regular water changes with very low alk salt water. Take your normal salt water, reduce the alk to, say, 1-2 dKH, , re-aerate to drive off the CO2, and use it for water changes.

 

[User]

Thanks Randy

Im going to order a second Alk test kit and fresh Hanna reagents, then grab some Sodium Bisulphate to drop alk in my WC water.

there’s a possibility I contaminated my Hanna reagent with a dirty syringe tip. I feel stupid if that’s true, being a Bench research biologist for 22 years...

 

[User]

Quick update- did the retests with new reagent etc and it’s definitely up there at 13.8.

mom making a new batch of saltwater and will lower alk to 5 using sodium bisulphate. This’ll get me down to target of 11 dKh with 4 x 10% water changes that I will perform over the course of three weeks.
Once stabilized I will continue to treat my WC water based on the dKh of the tank at that time, monitoring until my coral load depleted as expected and I finally turn on my calcium reactor

thanks!