Question

TimReef · Mar 25, 2017

I tested my water on 3/23
Alk:8.4
Calc:390
Mag:1400

Today I'm doing a water change I am only taking out 4 gallons/36 total gallons.
How is the water change going to screw up my parameters?

Also I buy my Saltwater from a Saltwater fish store

Flippers4pups · Mar 25, 2017

What type of tank are you keeping? FOWLR? Reef tank?......

To answer your question, test your newly made saltwaters parameters

Randy Holmes-Farley · Mar 25, 2017

One cannot say what effect it would have without knowing the parameters of the new salt water, but unless it is far from you rtank values, that size change makes little difference.

Suppose it is 11 dKH and 430 ppm calcium, then the new values will be:

0.9 x 8.4 dKH + 0.1 x 11 dKH = 8.66 dKH
0.9 x 390 mg/L Ca + 0.1 x 430 mg/L Ca = 394 mg/L Ca

TimReef · Mar 26, 2017

Randy Holmes-Farley said:
One cannot say what effect it would have without knowing the parameters of the new salt water, but unless it is far from you rtank values, that size change makes little difference.

Suppose it is 11 dKH and 430 ppm calcium, then the new values will be:

0.9 x 8.4 dKH + 0.1 x 11 dKH = 8.66 dKH
0.9 x 390 mg/L Ca + 0.1 x 430 mg/L Ca = 394 mg/L Ca

So I just did a water change this morning and checked my alk and currently I'm at 12.6 (bad or good)?

I thought this was high and so I am going to check it tomorrow once I can focus better.

Randy Holmes-Farley · Mar 26, 2017

TimReef said:
So I just did a water change this morning and checked my alk and currently I'm at 12.6 (bad or good)?

I thought this was high and so I am going to check it tomorrow once I can focus better.

That's probably an indication that you do not need any dosing of any kind, and the tank will reflect the salt mix.

What is in the tank?