Setting up an aquaponics system may not be difficult in itself. But getting it to successfully sustain itself can take a bit of trial and error. There are a number of factors that need to be just right – and since these factors vary from place to place, you need to be careful when you first set the system up. But there are other factors that are within your hands, and these you should take care of right at the start. And one such thing – also the thing that we are going to be looking at today – is aquaponics fish tank size.
The size of the tank that you are using is very important. And this is because 2 very big factors depend on it:
- The size of the tank determines how many fish you should be keeping in it.
- The volume of water in the tank (with the right number of fish) also determines how much grow bed the water can supply. Too small a tank and your plants will wither for want of food, and too big a tank, and there will not be adequate filtration.
Tank size vis-à-vis Number of Fish
The amount of fish doesn’t need to be very exact. But the health of your fish depends on the space they are able to get. However, with an aquaponics system, the equation is somewhat more complex. Since you will not be filtering the water artificially, your tank needs to produce enough waste for your plants. So allowing too much water for each fish means that there will not be enough fish!
Now, when you are considering the fish for your aquaponics system, here are the indexes to keep in mind:
- The first case scenario is when you are keeping your fish as ornamentation – and after the plant growth mainly. Here, the fish yield is secondary to the growing plants. And if you want to give your fish some space, you can store as little as 1 fish (about a pound in weight) to every 5 gallons of water. In other words, the ratio is a pound of fish to every 5 gallons of water – for smaller fish you’d be able to fit in more according to that standard. This is a pretty standard ratio – and will in most cases be able to sustain a balanced tank and grow bed system.
- On the other hand, if the fish yield is what you are after –and you are looking to rear more fish, then the ratio can actually be increased. The more conservative ratio is a pound of fish to every 3 gallons of water. You will be able to fit in more fish using this system – but you also need to care more for such a system. It is important to note that this ratio works very well for tilapia farming.
Volume of water vis-à-vis size of grow bed
Now this is an equally big concern. The aquaponics system works on the principle of the fish waste becoming food for the plants. In this way the plants thrive. On the other hand, the plants also act as powerful filters and clean the water for the fish. Fish waste buildup in the water is actually toxic for your fish and causes them to die out. So, adequate filtration is absolutely essential. And that is only possible if there is enough grow bed with plants to recycle the amount of water in your tank.
And in terms of volume, you should ideally have a 1:1 ratio between your fish tank and grow bed area with 12” depth. This roughly translates to 1 square foot of grow bed for every 6 gallons of water. Otherwise, there will not be adequate filtration of the water, and your fish are at risk
The general rule of thumb then is – 1 square foot of 12” grow bed needs 6 gallons of water with about 1.5-2 pounds of fish in it. This rough ratio should take care of your system.
So now all you need to do is determine how much grow bed you will be working with, as well as how many fish you plan to rear. And accordingly determine the volume of water you need. Once you have that worked out – you should easily be able to determine the ideal aquaponics fish tank size for your intended system!