Using Tap Water in Aquaponics Safely

by Roger Loper

Of course! This is one of the most common and important questions for newcomers to aquaponics.

The short answer is: Yes, you can use tap water for aquaponics, but you MUST treat it first to remove chlorine and chloramines. Using untreated tap water can be disastrous for your system.

Here’s a detailed breakdown of why and how to do it safely.

1. The Problem with Tap Water: Chlorine and Chloramines

Municipal water suppliers add disinfectants to our drinking water to make it safe for humans by killing harmful bacteria and pathogens. Unfortunately, these same chemicals will also kill the beneficial bacteria (nitrifying bacteria) that are the absolute heart of your aquaponics system.

  • Nitrifying Bacteria: These bacteria (primarily Nitrosomonas and Nitrobacter) are responsible for converting toxic fish waste (ammonia) into nitrites and then into nitrates, which are a usable fertilizer for the plants. Without them, ammonia will quickly build up and kill your fish.

There are two main disinfectants you need to worry about:

  • Chlorine: The older, more volatile disinfectant. It can off-gas (evaporate) naturally if water is left to sit for 24-48 hours. Aeration (e.g., with an air stone) speeds this process up significantly.
  • Chloramines: A more stable compound made by combining chlorine and ammonia. It is now used by many more municipalities because it doesn't off-gas easily and remains in the water longer. Letting water sit will NOT remove chloramines.

Using water containing either of these will crash your biofilter, halting the nitrogen cycle and causing an ammonia spike that can kill your entire system.

2. How to Make Tap Water Safe for Aquaponics

You must use a water conditioner (dechlorinator) designed for aquariums or aquaponics. These are readily available at any pet or aquarium store.

  • What to buy: Look for a conditioner that explicitly states it neutralizes both chlorine and chloramines. Most modern products do this, but you must insure that what you use is not only fish safe but that the fish and plants will remain safe for human consumption. The link below will take you to what we recommend and it is good to have on hand even if you typically gas off the chlorine. If you have a water leak and need to fill your system quickly to keep fish from dying, this product reacts instantly to remove chlorine and chloramines.

o    TrueNute - Chlorine and Chloramines Remover

  • How to use it: Follow the dosage instructions.
  • Procedure: The best practice is to treat the new water in a separate container (like a barrel or bucket) before adding it to your system. This is especially important when doing a large water top-up or change.

Alternative Method (For Chlorine ONLY):
If you are 100% certain your water provider uses only chlorine (you can call them and ask), you can aerate the water vigorously with an air stone for 24 hours or let it sit in an open container for 48 hours. However, using a conditioner is always the safer, faster, and more reliable method.

3. Other Tap Water Considerations

Beyond chlorine/chloramines, you should also be aware of:

  • pH Level: Tap water pH can vary widely (often between 7.0 - 8.5). You will need to test your tap water's pH and then adjust the pH of your entire system slowly over time to fall within the ideal range for your fish, plants, and bacteria (usually a compromise between 6.0 - 7.0), we recommend trying to hold at 6.8 for the best results.
  • Hardness (GH & KH): The mineral content in your water (calcium, magnesium, carbonates) affects pH stability (KH) and provides important nutrients for plants. Hard water is generally beneficial in aquaponics. Very soft water may require adding minerals.
  • Heavy Metals: While rare in treated municipal water at levels harmful to humans, trace amounts of copper or zinc from pipes can accumulate and become toxic to fish over time. A good water conditioner will also often neutralize these heavy metals.

What About Well Water?

Well water is an excellent choice for aquaponics as long as it is tested. It contains no chlorine or chloramines. However, you must test it for:

  • Pesticides/Nitrates: If you are in an agricultural area.
  • pH and Hardness: Can be very high or very low.
  • Dissolved Gasses: Well water can sometimes be low in oxygen or high in carbon dioxide or even hydrogen sulfide (smells like rotten eggs). Aerating it vigorously before adding it to your system will solve this.

Summary: Best Practice

  1. TEST YOUR TAP WATER: Use an aquarium water test kit to understand its pH, GH, and KH.
  2. ALWAYS TREAT: Before adding any tap water to your system, treat it with a quality water conditioner that removes both chlorine and chloramines.
  3. TOP UP SLOWLY: When adding treated water to replace evaporation, add it slowly to avoid shocking the fish with a sudden temperature or pH change.

In conclusion: Yes, tap water is perfectly fine for aquaponics once it has been properly conditioned. Using a dechlorinator is a simple, inexpensive, and non-negotiable step to protect the vital bacteria that make your ecosystem work.

 

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