Trying to understand phosphates, alkalinity

[docforestal]

Hello, did not find in a search, read a few earlier articles, but I admit to middle age affecting my focus and it seems my memory of chemistry is essentially gone

background:
new tank - 55 gallons,9 weeks old, cycled with bacteria in a bottle, fish in tank now 3 weeks, admittedly feeding heavy, trying to sort appetites, perhaps should keep to meats and avoid flakes.
No sump but small hob fuge for carbon,gfo and macro algae, currently gracillia , handful out q 2 weeks- small effect, I know
Small bullet 3 aquamax hob skimmer, full cup of yuck q 2-3 days

Since feeding the fish my phosphates have risen, up to 0.24, down to o.12 after 48 hours gfo
1 week later 0.29
Gfo back in

alkalinity has kept around 9.2 (salt mix numbers) and calcium ~500
1 week later alk is 8.8

are phosphate and alk related, other than phosphate inhibiting calcium carbonate formation?
Will dosing small amount of kalkwasser q3-7 days create meaningful effects lowering phosphate, as long as alk and ph stay in range?

I am working on better feeding strategies to keep fish well fed but not overdoing it, snails and crabs are keeping things clean
My hair algae is very pretty :) but getting better with CUC and a sea hare, in a week ~ 20% reduction so far

thanks for time and thoughts.
Cheers

 

[docforestal]

I forgot to mention, no corals and start of coralline is seen

 

[Randy Holmes-Farley Verified Community Expert]

Instead of answering a question (alk/phosphate relationship) that is complicated and likely not that helpful for your situation, let's address the issues you have.

Alk declined 0.4 dKH in a week. It is totally normal for alk to decline in a reef tank, even up to several dKH per day, so 0.4 dKH in a week is a very low demand and easily offset with a little baking soda.

Your phosphate is not an urgent situation, but there are lots of ways to lower it. I would not elect limewater (kalkwasser) as a good method for you8 since you have very low alk demand. Stopping GRFO and having it pop up again is also normal, and will happen with any method you elect.

IMO, your options are ignore it for now, continue the GFO, or start another method such as growing macroalgae.

The best choice may depend on the current nitrate level. Have you measured it?

 

[docforestal]

Hi Randy , thanks for the response - my nitrates are 10-20 - typically hit 20 after a week then i do a 15 gallon water change, and they go down to 10.

 

[docforestal]

I will mention , I just found your plethora of articles and am reading them up, to get a better sense/level of knowledge on this
I want to have the knowledge and systems & stability in place before adding corals to the tank - i plan to use kalkwasser solution for supplementation unless i get high demand (unlikely for a while) and doing it manually until demand is high enough to add to my top off water.
Thanks for all of your articles, lots of reading for me to do :)