In aquaponics we work with an aquatic ecosystem. The water is circulating through different parts of the system where fish, bacteria and plants are able to live. Unlike a classic garden, the water of an aquaponics system remains into the system. From the water perspective it is called a close system. An aquaponics system is known to consume 10 times less water than classic aquaculture and gardening. That said we still have some water consumption from the following points:
Fish and plants growth
Fish and vegetables are mainly composed of water (70 to 90% water). A setup well balanced and placed in a good sun exposition can produce a very significant quantity of food (twice more than a classic garden). When you harvest your crop, you physically remove water from your system.
Evaporation from the fish tank
The higher the temperature is and the more the water will naturally evaporate into the atmosphere. It is often better to keep the fish tank slightly covered. It will keep the direct atmosphere close to the tank saturated in moisture and minimize the evaporation.
Evaporation from the plant leaves
Plants are constantly evaporating water from their leaves. It helps them to raise the sap from the ground to the top leaves. The leaves evaporation will be influenced by the quantity of sun and wind. Sun is a key factor to the plants growth and especially photosynthesis. Wind can be necessary for certain plant fertilisation but too much wind can damage the crop and is therefore not a good thing. Try to position your setup in a low wind spot to limit the water evaporation (see the video the best position for your aquaponics here: https://youtu.be/i5dwtx0KjN0 ).
Evaporation from the growbed
Evaporation can also happen from the growbed but is generally limited thanks to the media. We generally want the media to reach 3cm above the maximum level of water. It insure that the media surface is dry and the evaporation is limited.
Water change sometimes necessary for nutrient balance
A setup perfectly balanced will recycle all nutrients. In practice the setup is never perfectly balanced. The nitrogen released by the fish and transformed by the bacteria will sometimes be higher than the plant needs. Your growbed and filters are able to stock some organic materials however the nitrate concentration will slowly and continuously increase. If you are in this situation you will need to renew some water. You can simply use some of your system water to water your classic garden.
How to top up the system:
As your aquaponics system water level will slowly decrease, you will have to fill it up some time to time. My recommendation is to not wait for half of your water volume to disappear before toping up the system. I actually recommend you to top up the system when 10% of the water volume disappear. This will prevent water parameter variation that could be dangerous for the whole ecosystem. (see the video about water for aquaponics here: https://youtu.be/kq8E4k_iEEU )
Welcome here! If you are new, you will probably be interested to discover Jonathan’s six steps to build and manage an Aquaponics system. Click here to access for free! Thanks and good reading 🙂