Effect on Ca/Alk/PH/Mg with evap

[latteslave]

Hi guys,

 

Realized recently that I was not checking my water change water for correct parameters after I tested out with high Ca (560) low Alk (6) - PH was OK (8.5) as was Mg (1300). I am working on bringing the alk up slowly with a target of 11 (at 9 today).

 

One issue I have is that the Oceanic I am using tests out over 540 on ca meaning even water changes won't bring this down. I have been researching other salts and thinking about Reef Crystals to get a higher alk and more reasonable Ca (batch I am mixing came in at 460)

 

On with the question - I know evaporation causes an increase in salinity. Does the evap also cause an increase in other values (alk, ca and mg)? or does the evap take those out (causing a decrease?) or do the levels stay constant?

 

I ask so that i can understand how to prep the top off water - If evap does not increase the levels, and I add in water with NO ca, mg, alk then I would effectively be lowering these with every top off. I propbably go through 3 gallons of top off a week.

 

Thoughts appreciated!

[AZDesertRat]

Only pure water evaporates so levels increase in the tank. You should be using only RO/DI for topoffs so adding topoff will bring the leves back to normal.

I would get my levels set right when the tank is fully topped off so minus any demands for calcium and alkalinity the levels should be back to normal when you top off. If your levels are increasing you are either adding pretty bad tap water or you are dosing unneeded supplements or additives, all of which is bad.

[latteslave]

Thanks for the answer on that - I am using RO/DI. I had not been dosing anything, just realizing that my WC had very high ca and low alk.

 

This answers what I needed, now just need to get the Ca down a little and will be good.

 

Thanks again!

[AZDesertRat]

Some Oceanic is high in calcium and low on alkalinity. I use Oceanic myself but have a big calcium demand so don't worry about it . I sometimes mix Oceanic and Instant Ocean for my smaller less demanding systems and it works well.