Nitrates, phosphates, nitrites, ammonia, and copper are about the only thing that you can easily test for - and probably worth measuring. Picking up a TDS
= total dissolved solids) and measuring the TDS
of the water will help you too - bigger numbers means there's lots of other crud in there that could really be anything.
But in the end - and this is from personal experience - even if your water tests "perfect", it doesn't mean it is. Our test kits just don't pick up trace levels of stuff that's in the water that will end up building up over time in our tank. In addition, just because the water tests fine one day doesn't mean it will be fine the next. For example, the incoming water to my house for 2 years has been around 80ppm TDS
, regardless of the season. Within the last 3 weeks, it's dropped to around 30ppm TDS
. That's a good thing... but it could've just as easily swung the other way. And why it did that... who knows.
The point is... if you want consistant water parameters in your source water, RO
is the only way to guarantee that. Do you need RO
to run a reef tank? No - plenty of people don't use it. But without it, you're at the mercy of a lot of factors (water department, seasonal water runoff, local fertilizer use by farmers, piping in your house, etc) that you have absolutely no control over.
Also... home filtration systems most likely strip the chlorine out of the water, and knock the big stuff out, but will most likely let a lot of stuff by. In testing my "Brita" water - with water from the tap at 80ppm TDS
, the water run through a Brita filter comes out about 45ppm TDS
. So yeah... it's taking some stuff out of the water, but leaving behind a lot.