Phosphate high, alkalinity low

[Carp890]

Morning people, I've got 100ltr redsea all in one peninsula tank. The tank is cycled 7 months. I do reg weekly water change gravel vac etc. Have a good clean up crew, 6 fish clown's nothing big all doing great. Soft and hard corals. I get my salt water from my fish store. 

My parameters have always been good, checked by me and the store (a very good store). Now all of a sudden my alkalinity has dropped to 6.7 from 9, and my phosphate has gone high 0.40ppm. I only feed frozen food twice a day. The tank looks great, also using rowaphos but it's not working I got it in the first chamber in  a media cup took the sock out ,is that ok?

Am I chasing number's or what can I do. I checked the shops water ph was 0,05ppm alk 7 any help appreciated 

[mcarroll]

If you're sure of your testing...

 

The alkalinity change is pretty significant – down from 9 to 7?  You'd want to double check your testing and then (if the result is the same) ask the shop about it.  Something is wrong.

 

Also, do you mean the shop has 0.05 ppm phosphates in their retail saltwater?

 

Phosphates aren't a problem per se for your corals or anything else.

 

But in general fresh made saltwater is not a place you want to see phosphate.  It would make me wonder which other "unexpected additives" might also be in there too.

 

If you have Poly-Filter available, it might be interesting to run one to see if it indicates anything other than brown/nitrogen.  

An ICP could be similarly revealing if that's available.

 

...if you're curious.  Otherwise just get with the store and ask if they can explain it....seems like you (they) could have a bad batch or something else going on.

 

 

[Carp890]

Thanks for the reply