<a href=showthread.php?s=&postid=9786171#post9786171 target=_blank>Originally posted</a> by Shagsbeard
There's a great article on this very question. Wish I had saved it. Someone with the link will show up with it shortly.
The two most important tests for a new tank are ammonia and nitrate. Nitrite is in there, but is typically not a problem in tanks... it's ok to test for it, but I found the test to be worth less than the other two. Next down the line is pH, but it's much better to have a meter rather than a test because pH can change hour by hour depending on all sorts of stuff. Get a pH meter rather than a test kit. Next I would get calcium and alkalinity. These are currently the only five tests I do... Ammonia, Nitrate, pH (should take my own advice and get a meter), calcium and alkalinity.
They say the next down the list is magnesium, but I'm just hoping that I get enough with salt and suppliments.