Alkalinity & Phosphate

I've had a 75 g tank up for two months and livestock in the last two weeks. My parameters are as follows:
Phosphate 8.2
Alkalinity 7
Nitrate 0
Nitrite 0
Ammonia 0

For the past month my salinity has hovered at 1.021 and has gone as high as 1.023 shortly after the water change. My problem was that my phosphate hovered around 7.9 and alkalinity fluctuated between 7 and 11 (most often at 7). I've topped off with store bought salt water to increase salinity with no luck and have added buffer to raise the PH to what it is now, 8.2. I understood PH and Alkalinity to go hand in hand but they are polar opposites it seems.
Two questions:
1. What could be causing my alkalinity to be so low?
2. How is it that my salinity isn't increasing to normal range of 1.023?

Thanks

 

pH and alkalinity do not necessarily go hand in hand.

pH is also controlled by how much CO2 is in your air and absorbed by the water. It is also controlled by other acids in the water.

The only way to safely increase your salinity is to use water mixed to the salinity you want to have and make changes with that water. I strongly recommend you mix your own water from your own RODI filter at home. Not all LFS maintain their RODI filters if they are even using RODI water.

 

back to the drawing board. any way to keep my alkalinity at or above 9?
I have glass lids on my aquarium btw

 

A glass lid will prevent the water from expelling CO2 and absorbing oxygen, resulting in a lower pH. FYI, phosphate and pH are not the same.

People often dose to maintain alk, but I'd suggest getting your pH problem figured out before fiddling with alk.

 

you can use Reef Builder by seachem, it will raise your alk, and not effect your ph.

Are you planning on having LPS or SPS corals? Because if you are you need to look into your calcium and magnesium levels as well.

If not, then you shouldnt have to be too concerned with your alkalinity as much, as long as you do steady water changes, that should maintain it at an acceptable level.

 

The glass lids are more than likely the reason your PH is low. You need proper gas exchange at the surface. As for the salinity what are you using to check it?

 

it makes a HUGE difference if you remove the glass lids. They cause so much problem. The best thing you can do if you want some sort of cover is to go to home depot or Rona or any home improvement store and get a bulk sheet of egg crate (found in lighting department) and cut out your own custom lid. It will allow the gas exchange you need and will prevent fish from jumping out.

 

You should measure your Magnesium and make sure it is at least 1320 ppm (better if it's around 1400 ppm). Low Magnesium can cause you to have problems maintaining Calcium and/or Alkalinity.

 

I'll get the egg crate stuff tomorrow I guess.

I'll also need a magnesium test kit. just got back from the fish store too.

 

Just make sure to ask for "light diffuser" when you are in the lighting department. If you ask for egg crate, they will look at you like you have two heads. Speaking from experience ;D