Here’s a few articles:
http://healthypets.mercola.com/sites/healthypets/archive/2013/09/09/struvite-stones.aspx
http://healthypets.mercola.com/sites/healthypets/archive/2012/01/03/fish-as-a-protein-source.aspx
Found this in the above article: “Last but not least, the magnesium content in fish has been linked to urinary tract diseases in cats. A diet overloaded with the mineral magnesium can predispose your kitty to magnesium ammonium phosphate crystals, also known as MAP crystals or struvite crystals. Crystals are a big problem for many, many cats.” Maybe geared more towards cats that eat alot of fish.
http://products.mercola.com/healthypets/bladder-health-for-pets/
This is the test strip I buy: http://www.amazon.com/PH-TEST-TAPE-Acid-Alkaline/dp/B0001SR4NM/ref=sr_1_2?s=hpc&ie=UTF8&qid=1413557089&sr=1-2&keywords=urine+ph+test+strips
