I thought I'd ask the question as a few others have, and make a discussion, hopefully with some scientific approach to it.
So, Can you use tap water to top-off a marine, or even reef tank with an algae scrubber?
For me, this is due to a few reasons:[list]My RO/DI unit isn't very efficient, roughly 5 parts waste water to 1 part pure water
It costs a lot in water bills!
As it gets warmer, and also due to the new fans in the sump to cool the lights for the scrubber, I'm using around 150l a month (40 us gal) in fresh water for top-offs. So 6 times that with the RO unit. It's a waste![/list]Firstly, I managed to dig up some old test certificates I got from our local water board when we had the shop (still live near by, so identical water), it's a few years old however, but you guys may find it interesting:
Test 1, tap water after leaving the water without using it in the building anywhere over night:
Test 2, tap water after flushing the water out of the tap for 5 minutes:
You'll notice the huge reduction in copper after flushing the tap, we, of course, have copper pipes, not great for corals, but is that level acceptable after flushing?
It was explained to me by the engineer from the water board, that phosphates are actually added to the water to counteract lead, as there were still a few lead pipes in the area apparently (I believe all the water mains in Canterbury are plastic however).
There is a test for chloride there, but not for chloramines, so I presume they don't add them, (I'll double check), so I could probably get away with letting a vat of water settle over night with an air curtain in there.
Nitrates are acceptable at 24-25 ppm, the algae scrubber should pull those out pretty easily.
So the questions:
Is the level of copper (0.03ppm) safe for fish and corals?
Is the level of lead (0.0005ppm) safe for fish and corals?
Is orthophosphate the thing we test for in marine tanks? In our water it's pretty high, at 2.2ppm, but should be taken out by the scrubber again.
Is it worth using a water conditioner? (e.g. Seachem Prime - love the stuff for the ammonia/nitrite/nitrate binding! plus a 5ml capfull does 200l!)
If fluoride is added to the water (I don't believe it is here yet), is it dangerous in the quantities they add to the fish/coral?
Will this help with calcium and alkalinity replenishment?
Let the discussion begin! (and if it is safe, experimentation)