Trouble to get my alkalinity up

[Tofi]

I have problem to adjust my alkalinity over 7dKH. It is staying between 6.4 and 7. Also i can not increase calcium over 400. I am using BRS 2 part mixing solution (adding 100 ml soda ash and 100ml calcium chlorine a day)
Because i was fighting with algae (probably my rocks which i get from guy who used them over 8 years leaks phosphate and i never can lower my phosphate under .08) - 2 month ago I had to do 100% water change put new man made rocks also 4 months ago i changed sand bad from DSB to 1.5 in.
My tank went through cycle (get diatoms)
I am using Salinity salt, carbon reactor, GFO reactor, skimmer, miracle mud, 75 LBS rocks.
My tank size 90G +25G sump.
Parameters:
Magnesium 1340
Phosphate 0
Nitrate and nitrite 0
calcium 400
alk 6.4
Ph 8.15 very steady
salinity 1.025
I have 2 medium size fish and 7 small size fish, some snails and one torch coral- everything looks good and healthy.
Do I have to worry about low alkalinity if I want to have more corals?
How i can increase magnesium?

 

[Tofi]

I mean How I can increase calcium

 

[mike007]

What size tank Is this? 100 ml alkalinity and calcium is a lot. I would have your test results double checked.

 

[redfishbluefish]

What size tank Is this? 100 ml alkalinity and calcium is a lot. I would have your test results double checked.

+1 (It's a 90G tank with 25 G sump)


Have your LFS or a fellow reefer double check your test results. Only have one coral and consuming all that calcium carbonate doesn't sound kosher. I too have a 90G mix reef with large mature hard corals and using the same concentration of alk and calc and only use 55 mls per day of each.