Using fresh surface water for saltwater tank?

Swingline77 · Aug 13, 2018

It's my understanding that fresh surface water often contains far less dissolved ions than well water, at least far less calcium. Also, a local fish store owner claims to have used well water as a base for saltwater tanks for years, without deionizing it.

I'm wondering if it's possible to use fresh surface water (lake, river, etc.) as a base for a saltwater tank. Minor problems with this approach would be the introduction of sediment and chemicals into a tank. In some areas, phosphates especially might be a problem. Overall, it doesn't seem like it would be too bad, though (https://www.ncbi.nlm.nih.gov/pubmed/10894537).

The big issue I'm concerned with is the introduction of disease/parasites. First, some things like Micobacterium marinum will already be in a saltwater tank. Second, many freshwater species will die in saltwater, and vice versa... but maybe not everything. I wonder if it's a realistic possibility that problematic organisms could be introduced from fresh water.

Getting surface water is appealing. I think that in my state I'm legally allowed to take 20 gallons a day, but I have to check. Filling up a gallon every day on my way home from work sure beats buying, setting up, maintaining, and paying for an RO system.

Ranjib · Aug 13, 2018

I personally think its not worth the risk. You have to do some checks/tests before using it. Remember most surface water composition has some seasonal variation

sfin52 · Aug 13, 2018

@Randy Holmes-Farley

KrisReef · Aug 13, 2018

I used to have a spring that produced good quality water, zero Phosphates & nitrates that someone had installed a hose in and it gushed at about 1/2 gallon per second. I used it for years until I moved.

I would not use surface water myself because I would be concerned about runoff or aerial contamination.

Testing your surface water each time is going to be more costly than an r/o unit. Plus r/o is a shorter haul from the source.