ALK consumption, does this make sense

[hoffmeyerz]

My ALK has been low for quite some time (dropping at times to 5.5 dKH) and I never really knew why. To be honest I didn't really worry about it much since my pH was ok and I don't have any coral, it's FOWLR right now.
I decided I would address the issue and added Randy's diy alk solution of baked baking soda to raise the ALK. It took 60ml total to raise it 1dKH to 7. It has since then dropped .8 over three days. The only thing I can think of that's doing that is the small amount of what appears to be Coraline algae in the tank. It hasn't spread much in the last few months but I'm assuming that's because of the low ALK.
By my figures it looks like I'll need to dose 15 ml daily to keep the ALK up, tank is about 80gal total volume. Does this seem about right/make sense?

 

[Randy Holmes-Farley Verified Community Expert]

My ALK has been low for quite some time (dropping at times to 5.5 dKH) and I never really knew why. To be honest I didn't really worry about it much since my pH was ok and I don't have any coral, it's FOWLR right now.
I decided I would address the issue and added Randy's diy alk solution of baked baking soda to raise the ALK. It took 60ml total to raise it 1dKH to 7. It has since then dropped .8 over three days. The only thing I can think of that's doing that is the small amount of what appears to be Coraline algae in the tank. It hasn't spread much in the last few months but I'm assuming that's because of the low ALK.
By my figures it looks like I'll need to dose 15 ml daily to keep the ALK up, tank is about 80gal total volume. Does this seem about right/make sense?

0.3 dKH per day is not that much.
Is nitrate accumulating? That can deplete alk.

 

[hoffmeyerz]

My nitrate has risen some as I've added some livestock over the last month. It used to hang 12-15 and now 18-20. My ALK was low previously though hanging around 5.5dKH with water changes being the only thing that slightly increases it.
I'm trying to find a way to lower my nitrates. I run a Lifereef sump and skimmer and I think my bioload right now is low for the skimmer. I only have six small fish fish in the tank right now (75gal), when I do tank maintenance and stir things up I get a good foam and it skims well but on a normal daily basis it's a very minor foam if at all.
Parameters as tested today:
Specific grav: 1.025
NO3: 18.8
NO4: .05
ALK: 6.2 dKH (60ml alk solution added 3 days ago)
Bio load is 3 pajama cardinals, 2 clowns, bicolor angel, a snowflake eel, and one hermit crab (plan to add more but wanted to make sure eel was happily fed and not bothering them first)