Tap Water?

[Sandy Andy]

I've recently set up a ten gallon tank four weeks ago and filled it with dechlorinated tap water. I am strongly considering getting an RODI system soon. Can I keep the tap water in my tank and replace it with RODI water gradually over time as I do my water changes? I've heard that tap water doesn't really harm the fish, but can cause an algae spike. If the fish are not going to get any diseases or die from the tap water, then I think I can wait till I get that RODI system. I don't want to have to restart my tank because I am already so far into the cycle.

[Humblefish]

Is there currently any livestock in your tank? If not, drain the tank and refill with RODI saltwater. It won't significantly impact your cycle because most of the nitrifying bacteria live in the rocks & sand. Being out of water for even 30 minutes isn't going to kill a significant amount of bacteria.

 

Tap is sometimes fine for fish and even soft corals/LPS. (Every municipality has different quality tap water.) However, the endless battles with nuisance algae due to high phosphates will drive you mad.

[Sandy Andy]

I already have three hermit crabs and I don't have an RODI system at the moment.

[Sandy Andy]

I've been using tap water with my previous freshwater tanks and I didn't see algae blooms. Maybe a little on the glass, but it was easily wipeable. Considering that I've gone for a long time without an algae blooms using tap water, I think I can go a few months without a bloom. 

[mcarroll]

On 3/24/2020 at 8:49 PM, Sandy Andy said:

I've recently set up a ten gallon tank four weeks ago and filled it with dechlorinated tap water. I am strongly considering getting an RODI system soon. Can I keep the tap water in my tank and replace it with RODI water gradually over time as I do my water changes? I've heard that tap water doesn't really harm the fish, but can cause an algae spike. If the fish are not going to get any diseases or die from the tap water, then I think I can wait till I get that RODI system. I don't want to have to restart my tank because I am already so far into the cycle.

Folks used to use tap water much more frequently than they do now.....it can work fine, but there are some known and unknown risks.

 

Those risks vary with your locality....some locales are better or worse and some are more or less risky.

 

If you know your local water, it might be both fine and safe.  

 

But the unknowns (most of us don't know anything at all about where our water comes from) are what drives most of us to make or buy purified water.

 

And it may be worth stating explicitly:  Some tap water is very inappropriate for reefing with mineral levels that can actually cause your salt mix to malfunction or it can potentially have other harmful additives.