Here is my personal opinion on test kits, and yes I know some of you are not going to like this:
Salifert kits (none better)
pH (I suggest a meter as well and calibrate it often)
Ammonia (unnecessary)
Nitrite (won't use much after initial cycle)
Nitrate
Calcium
Alk
Mag
iodine (don't waist your money)
silicate (forget about it)
Phosphate (nope)
Strontium (nada)
Here is why I say skip Ammonia, Iodine, Silicate, Strontium, etc...
If you need to test these take a water sample to you LFS and have them test it, ammonia will usually come and go so fast you won't catch it anyway. These rarely if ever change with quality, routine water changes.
Now if you really want to know about Phosphates in your water, get one of these:
http://item.express.ebay.com/__Pet-S...mdZExpressItem
They are the ONLY way to really get an accurate reading of your phosphate levels in your tank. 90% of the time a simple test kit for phosphates will show no color change and remember they are only testing one type of phosphate in your tank.
My suggestion, invest in a good refractometer, a TDS meter, use RO/DI water and change filters when TDS is 3 to 5 ppm or greater, do routine water changes, topoff water should be RO/DI as well.
This is my experiance: I bought all the test kits, I have used the ammonia maybe 3 times, Nitrite maybe 10 times, Nitrate 1 a month. Calcium and Alk I've gone thru 4 of them, I test these two more than anything. Mag, maybe once or twice a month. For pH I have a test kit and a meter, if I think the meter is not right I test it with the kit to see and I usually calibrate my meter twice a year. At 15.00 to 30.00 a kit if you are going to use it a few times why spend the money?
JME