Alkalinity keeps droping

[Donald Wright]

I have an issue with Alkalinity in my 220 Reef Aquarium, I can't get it to stay above 6.66 dkh. Here are my water parameters :

Calcium 440 to 460, steady on a drip feed daily of Kalkwasser
Magnesium 1360, steady all the time
Phosphates- 0-
PH- varies between 8.0 night and 8.2 day, electronic probe monitored ,
Temp steady at 25 Celsius
Alkalinity, 6.66 with a drip feed of Liquid Soda Ash, twice the recommended ml for a 1.4 dkh daily increase
If I lower the drip feed to recommended amount of Soda Ash the dkh will drop to approx. 4.8 to 5.5
Have CO2 remover media to help with PH, feed into Skimmer.

No loss of fish or corals, soft corals only but will shrink when dkh is below 5.

Problem is the more Soda Ash or Sodium Bicarbonate added the dkh will increase but drop off rather quick when not a heavy drip to tank all day. Large white deposits will form on pumps, heaters and skimmer when this high dose of Alkalinity additive is added to the tank. I have had pumps stop working from the armature getting coated with the deposits.

the tank is full of Live Rock from Fiji, has been in the tank for more than 15 years.

I have RO unit feeding the top off at a 7.0 ph of fresh water.

Does anybody have any ideas on how to increase the dkh without causing all the equipment to get coated with heavy white deposits?

 

[AngryMike2016]

If you're doing those calcium and alkalinity dosings closing in timing to each other, you could be causing precipitation.

 

[Donald Wright]

If you're doing those calcium and alkalinity dosings closing in timing to each other, you could be causing precipitation.

all drip feeds are at least an hour apart from Alk and Kalk

 

[Bastray]

If I was in your situation I would switch over to 2 part. I personally use ESV. Figure out the dose you need to increase your ALK and do it slowly over a week or so. 2 part is pretty straightforward, simple to dose, you can add it on a dosing pump later on if you want to automate it, and considering you dose both parts equally you make sure that your tank is balanced. Others I am sure will have different opinions, but my tank became much more stable since dosing 2 part using a dosing pump. I also don't get any residue in my tank from 2 part. When I started my tank I was not dosing a balanced amount of 2 part and my ALK was low and calcium was high and no matter what I did I couldn't fix it, until I dosed in equal parts. Eventually my ALK went up and my calcium balanced out in range. Randy Holmes Farley has some good write ups on ALK/CAL balancing in the tank if you search around here in the forums.

 

[Donald Wright]

Thanks for your input on this, I did have my system on two part thru BRS, I tried using equal amounts but either the Calcium went thru the roof or the Alkalinity just kept dropping. I had to stop this because of the heavy white deposits causing my pumps to fail. I had to keep increasing the Alkalinity about every 3 days to just keep it from dropping. I switched to Kalkwasser and now have my Calcium under control and stays level at 460.

I did find out last night looking thru my programmed settings on my dosing pumps that they over lapped in the middle of the night for an hour, this may be what was causing all my issues. I have changed the programming now so at least a hour apart from dosing Alkalinity and Kalkwasser. I also added a little more Magnesium to bring up some, have been steady at 1340 so will bring it up to 1450 to see if this also helps stabilize the issue.