Tap or Filtered Water for a Reef?

[kien]

As already stated numerous times before me, there are people who are successful with tap water and with RO water, reef or FOWLR. This is one of my favourite tap water Mixed Reef tanks. Mind you, he has recently switched over to using RO but was very successful with tap water for a long time and never had any issues with tap water in his reef (that I'm aware of).

So yes, you can use tap water successfully so long as you are doing everything else right The one big downside to using tap water though is its consistency as was mentioned. Ultimately if you use tap water you don't really know what is going into your tank. Whereas if you use RO, you know that it is water, period (so long as your TDS is zero). I think this is the biggest reason for using RO.

[globaldesigns]

I RO my water, personally I don't feel DI is worth it. I have a TDS reading of ZERO with just RO filtering. Why take a chance of algae, you may have enough issues with beating the algae without adding tap water to the equation.

[Rogue951]

I use RO water, my TDS meter reads 0 so that's good enough for me.
Tap water is somewhere between 5-10.
I have noticed in my earlier days of reefing that when I used to top up my tank with a cup of tank water I almost immediately noticed a bloom of hair/film algae and diatoms.
so since then I've invested in a filter.

It also has to do with what the water goes through to get to you.
If you live in an old area with old pipes no matter if the water coming in is crystal it's going to leach into the water. so those who use tap water and have no problems are extremely lucky.

In Vancouver we are said to have the best water in the world, and I believe it too. however in a recent news story it showed how despite city testing at the plant, some areas with old/poor piping had severe water problems including smell and discoloration.

I guess what I'm trying to say is RO eliminates any doubt and inconsistency in water parameters.

[Magma]

the large reef tank at Big Al's near the High Tech Section is all Tap water it looks amazing, myself I use tap water, no problems other than a few small cyno outbreaks and in my new tank a big diatom bloom nothing that wont be cleared up with a little TLC.