Alkalinity

[chrispycritter]

Hello everyone im currently dosing AFR and found lately alkalinity is lower 7.4 to 7.8 would like it above 8 would be alright to set up another dosing pump and add soda ash ? My other parameters seem to be steady mag. 1240 to 1260 cal. 410 to 420 ph 8.0 to 8.3 specific gravity 1.025 currently dosing 100ml. All for reef daily and if i done my math right thinking 50 ml soda ash daily. Its 240 gallon system with montipora coral and a few bird nest hoping to get into acrapora soon.

 

[ShakeyGizzard]

Hello everyone im currently dosing AFR and found lately alkalinity is lower 7.4 to 7.8 would like it above 8 would be alright to set up another dosing pump and add soda ash ? My other parameters seem to be steady mag. 1240 to 1260 cal. 410 to 420 ph 8.0 to 8.3 specific gravity 1.025 currently dosing 100ml. All for reef daily and if i done my math right thinking 50 ml soda ash daily. Its 240 gallon system with montipora coral and a few bird nest hoping to get into acrapora soon.

I use Instant Ocean Reef Crystals, the dKH is around 10 of this salt mix, maybe you can check the parameters of the salt you are using and with the right salt, any needed dosing would be at a minimum. but if you change salts, do it slowly with a ratio mix as you go

 

[Peer.Boerner]

Maybe consider pharma grade sodium bicarbonate? Raises ALK with little adversity. Soda Ash also very effective but more aggressive. Let us know what you do.

 

[Randy Holmes-Farley Verified Community Expert]

Just up the AFR dose. No need to mess around with different additives unless you want to switch away from the AFR.

 

[aussie_aquarium1]

Soda ash is fine for what you're doing, chemically it's the right pick if you want to nudge alk without dragging pH down. But I'd ask one question first: when's the last time you bumped your AFR dose rate?

AFR is balanced, so if your alk is consistently sitting at 7.4–7.8 instead of 8.5+, the simplest read is that you're under-dosing AFR overall. Your corals are probably consuming slightly more than the bottle's "standard" rate suggests. The fix is to step the AFR up by 10–15% and re-test in a week. If alk lands where you want, no second doser needed!

If you've already pushed AFR up and alk still won't climb, then yes, second doser with soda ash, dosed separately.

A few notes if you go that route:
- Mix soda ash at ~70 g/L RO/DI. One mL of that solution moves ~0.014 dKH per US gallon of net tank water. So bumping a 100 gal from 7.6 to 8.4 (a 0.8 dKH lift) is ~57 mL of stock solution total, spread across 3–4 days at ≤1 dKH/day.
- Drip it slowly (most people split into 6–12 doses/day) rather than slug it. Soda ash will spike pH locally if dumped.
- Dose it in a high-flow area, not next to the AFR drip point.