Removing Chlorine and Chloramines from Water

by Peter
(Twin Cities, MN)

Is it safe to use aquarium dechlorination chemicals to remove chloramines and chlorine from tap water for plants that will be consumed, and is water so treated good in general for a hydroponic garden?

Answer:  Peter- fish are like a canary in a coal mine...if something used in the aquarium is even slightly toxic, the fish are likely to die. Even high nitrate levels and incorrect salinity levels can kill fish. One time, in a pinch, I used an aquarium pH test kit to check the pH of my hydroponic system. I than used aquarium pH down to lower the pH of my nutrient solution. I did so with a degree of confidence, using this same line of reasoning. In this instance, my plants never showed any ill effects from the treatment and I had no reservations about consuming the produce.

Obviously, the chemicals used to adjust the pH in a fish aquarium are different than the chemicals used to dechlorinate tap water. In fact, the chemical in the pH down was a plant fertilizer! I don't have any personal experience with dechlorination chemicals....however, a quick search on the internet led me to a list of the most popular dechlorination chemicals. They are...

Sodium thiosulfate (solution)
Sodium sulfite (tablet)
Sodium metabisulfite (solution)
Sodium bisulfite (solution)

Seeing as how these substances are safe to use around fish, I would assume they are relatively harmless in a hydroponic system as well....but we can go one step further than that. Sodium bisulfite and Sodium metabisulfite are both substances used in wine making to sterilize the must. They work by releasing sulfur dioxide, which gasses out of the solution and dissipates harmlessly into the air.

Given the very similar chemical formulas of the other two substances, their action would be the same. The chlorine in your water would either combine chemically to the Sodium to form Sodium Chloride (table salt), or else would become destabilized by the action of the added chemicals, causing it to de-gass from the solution. I don't know which is the case, but either way the reaction is harmless.

It is always more healthy for your hydroponic garden to use dechlorinated water than to use fresh tap water. On one hand, I am very confident that using dechlorination chemicals will have no detrimental effect on the plants or the hydroponic system, nor will it affect the consumability of the plants produced.

On the other hand, leaving the water out for at least 24 hours exposed to open air (in a big plastic storage tote, for example) will allow the chlorine compounds to de-gass naturally from the tap water. This method also allows the water to come up to room temperature, which eliminates the possibility of any damage from temperature shock. I have used this method for years with excellent results.

And while getting rid of the Chlorine compounds is healthy for the plants, in all honesty it is the Fluoride compounds (in the water) that us humans need to be worried about!