What to do when baking soda not raising alkalinity

[MarcoReef]

Dear Randy, I had a successful tank running for many months with great acro growth but since a couple of weeks I am struggling to keep alk from dropping. I am trying to raise alkalinity using a solution of water and baking soda but alkalinity continues to drop, today it went below 7. Last week I was able to stop the drop / maintain alk by dosing manually sodium bicarbonate powder vs the solution, but this is only a workaround. I remember a post of yours from many years ago when you mentioned nucleating sites for precipitation and a cycle hard to stop. Is a massive water change the only solution to find a new equilibrium for the tank? Why dosing a solution of water and baking soda is not having an effect on the tank?

 

[Randy Holmes-Farley Verified Community Expert]

There’s likely nothing wrong except not adding enough. How much did you add?

 

[MarcoReef]

Dear Randy, thanks for replying. I estimate my mix reef tank to contain approximately 450liter (100 gallon) and it is quite heavily stocked with corals and fish. Up to last week I was dosing 120ml/day of a solution of 80g/liter of sodium bicarbonate (80g was the max I could dissolve in 1 liter of room temperature RODI). As I was unable to raise KH, I switched to a solution of 60g/liter of baking soda (I simply baked 300g sodium bicarbonate for 45 minutes in the oven and then mixed in 5 liters osmosis water). I started dosing 60ml/day of this new solution assuming it was a ‘stronger’ buffer - but as KH continued to drop, I gradually increased the daily dose until I arrived 2 days ago at 150ml/day but still seeing KH drop to below 7. So either the DIY is not ‘’potent’’ enough or it is precipitating (white cloud appears when I manually dose). As last night I noticed some SPS starting to suffer, I manually dosed a tea-spoon of baking soda powder directly into sump, stopped dosing the DIY baking soda solution, and reverted back to using the ‘’old’’ Triton Core 7 KH buffer which I dosed in the past before moving to my DIY solution (I don’t know what the Triton buffer contains). Overnight I dosed 50 ml of the old Triton solution + 1 tea spoon baking soda powder and this morning the KH raised from 6.9 to 7.4. Additional info – my CA is around 410, and MG around 1480 so I don’t think KH is limited by MG. I kindly ask your help to determine what I should do in order to raise / maintain ALK using exclusively a DIY solution of baking soda – thanks!

 

[gbroadbridge]

Dear Randy, thanks for replying. I estimate my mix reef tank to contain approximately 450liter (100 gallon) and it is quite heavily stocked with corals and fish. Up to last week I was dosing 120ml/day of a solution of 80g/liter of sodium bicarbonate (80g was the max I could dissolve in 1 liter of room temperature RODI). As I was unable to raise KH, I switched to a solution of 60g/liter of baking soda (I simply baked 300g sodium bicarbonate for 45 minutes in the oven and then mixed in 5 liters osmosis water). I started dosing 60ml/day of this new solution assuming it was a ‘stronger’ buffer - but as KH continued to drop, I gradually increased the daily dose until I arrived 2 days ago at 150ml/day but still seeing KH drop to below 7. So either the DIY is not ‘’potent’’ enough or it is precipitating (white cloud appears when I manually dose). As last night I noticed some SPS starting to suffer, I manually dosed a tea-spoon of baking soda powder directly into sump, stopped dosing the DIY baking soda solution, and reverted back to using the ‘’old’’ Triton Core 7 KH buffer which I dosed in the past before moving to my DIY solution (I don’t know what the Triton buffer contains). Overnight I dosed 50 ml of the old Triton solution + 1 tea spoon baking soda powder and this morning the KH raised from 6.9 to 7.4. Additional info – my CA is around 410, and MG around 1480 so I don’t think KH is limited by MG. I kindly ask your help to determine what I should do in order to raise / maintain ALK using exclusively a DIY solution of baking soda – thanks!

When you bake baking soda (sodium bicarbonate) you end up with sodium carbonate.
Sodium Carbonate is much more soluble in water so you can make a more concentrated solution. The solution that you have made is quite weak.

I use 100g per litre, which I think is about the same strength as Randy's recipe, but you can easily go to 200g per litre if you wish.

I don't know the composition of the triton Core KH buffer, but I would suggest that you simply need to make a stronger solution or dose more of what you have already made.

 

[MarcoReef]

Thanks. As I made a batch of 5 liters with 60g/liter of baking soda, can I simply add more sodium bicarbonate to the solution and bring to the boil for 5 (?) minutes so that the incremental bicarbonate dissolves into carbonate?