Aquaponics Home System – Part 18: Selecting Fish and Plants

In this project we’re combining traditional fish keeping in an aquarium, and growing plants with the roots submerged in the same water as the fish live in. The question to answer next is – what is the best water pH value to aim for?

Depending on the genus and species of the fish they’ll prefer different aquarium pH levels, and the same goes for the different plants that you would want to grow in such a system.

The chart below shows five different fish that are popular among aquarium people which means that they should be easier to find for sale. An aquarium forum is a great place to look if you want to buy fish online instead of via the newspaper, but it doesn’t matter if you find the coolest type if there are no fish for sale nearby. This is of course depending on where you live and more exotic fish are generally harder to find:

The chart also shows three types of plants that would be practical to grow in our aquaponics system due the fact that our plant tank is placed only 60 cm (24″) below the ceiling, so for instance climbing beans is out of the question at the moment 😉 Many types of herbs on the other hand would easily fit in if you have height limitations. Our  aquarium stand has a height of about 50 cm (20″) which means we have to raise the plant tank a good deal up in the air.

The purpose of the chart is to show that there is a pH level range in the middle where three types of fish and three types of plants are satisfied with the pH level at the same time, namely the pH range from 6.5 to 6.8 (Gold Acara, Blue Acara, Yellow Dwarf, strawberry plants, spinach and parsley).

Whether those particular fish are happy living together I’m not sure, but it’s a place to start. You probably wouldn’t want to mix in betta fish, or piranha or type like that 😉 Other types of pet fish we’re looking at right now includes Oscars (velvet cichlids), discus fish and tetra fish. Unfortunately Oscars are a bit too large for our particular aquarium set up, but the group of tropical fish is a good place to look for inspiration.

The point here is that by making a graph like the one above you can visualize what would be the best pH level for the system, no matter what fish or plants you throw in.

In the coming weeks we’re going to look further into the details of this new aquaponics system. I’m into computers so I would really like to be able to add a digital pH meter to the system and perhaps an orp meter too. That would make it much easier to take good care of the system if you can have live measurements running on a web page instead of making manual measurements.

Also, we have to take a closer look at which strawberry varieties will be best for aquaponics and which ones are available to us. We have talked about growing garlic but being a root crop I don’t think the chances of success are good. Blueberry would probably be a better choice – if we can manage the height 😉


Common name Latin name pH preferred Reference
Yellow Acara Aequidens metae 4.8 – 6.0
Gold Acara Aequidens sapayensis ? – 7.0
Blue Acara Aequidens pulcher 6.5 – 8.0
Yellow Dwarf Apistogramma borellii 6.0 – 8.0
Elliot’s cichlid Thorichthys ellioti 7.0 – 8.5
Strawberry 5.0 – 7.5
Spinach 6.4 – 6.8
Parsley 6.5 – 6.8

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