Should I Cover My aquaponic Fish Tank?

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Fishes are the most common aquatic animal used in aquaponics systems. Be it tilapia, jade perch or even gold fishes, they all perform the same function which is to provide nutrients for the plants.

Aquaponic fishes should be covered since the sun and rain if allowed into the tank, would tend to change the water quality which would in turn affect both fishes and plants.

Aquaponics uses the waste produced by the fishes to create nutrients for plants to grow. These nutrients along with the water quality tends to create the perfect environment for plants to flourish.

A good quality of water should be maintained at all times to ensure that the plants are getting the nutrients they need to grow. But how does weather conditions affect the quality of water? There are a number of ways water can be affected. So let’s find out!

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Should your aquaponic fish tank be Covered?

The water tank is the most open component of an aquaponic system and if not covered will have to withstand the full brunt of the weather.

Leaving the tank open would allow sunlight and rain to come into the tank. For one, the fishes would definitely not like the change in conditions from total cloud cover at one moment to total blazing sun the next moment.

So let’s talk about rain.
Depending on your location the amount of rainfall may vary and with this you will find yourself correcting the water quality as often as the weather changes.

Reason being is that, rain is slightly acidic at a pH of about 6.5.

The pH scale measures how acidic or alkaline something is.

pH is measured in a range between 1.0 to 14.0
1.0 being the most acidic, 7.0 being neutral and 14.0 is the most alkaline.

In aquaponics good bacteria converts ammonia in a two step sequential process, firstly to nitrites and then nitrates. Which is the nutrient plants use to grow.

This process is called nitrification and is a slightly acidic process causing the water to become more acidic when the process occurs.

Now think about rain being acidic and nitrification also being acidic. The result is a double whammy and can severely affect the water quality.

The unwanted happens. Plants and fishes die. If you do not have the tank covered and you take the reactive approach. You would find yourself correcting the water’s pH every time rain falls.

pH correcting chemicals cost money and at the end of the day we all want to setup an aquaponic system that is, well, stand alone. One which we have minimal input.

This tragedies can be prevented by simply placing a cover over the fish tank.

So now on to sunlight. That one thing that everyone loves including plants. So why is sunlight bad if it gets into the fish tank?

Although sunlight causes aquaponic plants to grow. It also cause algae in the system to grow also. Since the fish tank is the probably the biggest open part of the system. Here is where most of the water will be seeing sunlight.

As a result, you will find most of the algae growth will be here if the tank is not covered.
This is because algae are like miniature plants in their own rights and uses sunlight and nutrients from the system to grow.

As a result, the nutrient concentration in the system would be reduced which will in turn reduce tha amount of nutrients available for the actual plants to grow. Now what you find is stunted growth or even lack of growth by the plants in the system when this occurs.

Another ill effect of having algae growth is lack of oxygen. If sunlight and algae growth are allowed to get out of hand, the oxygen concentrations within the entire system will drop. With a lack of oxygen brings fish kill and also reduced plant growth.

It’s kinda hard to invest money into a system that is intended to feed your family or even bring in some income by allowing so much harm in by not applying this simple fix.

Next up temperature,

Temperature directly affects the pH of the water. The higher the temperature gets the more acidic the water becomes. This is because it’s easier for the water molecules to dissociate into hydrogen ions as water temperature increases.

As mentioned before an increase in water pH would cause fishes and plants to eventually die if not corrected in a timely manner.

Another issue that may arise is having a Clustered Fish stock. Fishes don’t like to be clustered and if held in a tank where there are a lot of other fishes, they would tend to leap out of the tank thinking it’s for the better.

What ends up happening is they fall helplessly onto the ground and eventually suffocate and die. Now that sounds harsh but that’s the reality of keeping fishes in an enclosed area.

Apart from things getting out, a protective cover would prevent things from also getting in. Leaves and debris have a away of finding themselves in unwanted spaces.

These foreign objects may cause plugging of outlet lines and filters. Line and filter blockage would cause the water level to build and overflow the fish tank resulting in water loss and failure of the system.

What should I use to cover my fish tank?

I have found that shade cloth can make really good covers. They

  • Can be cut to the dimensions of the tank
  • Can be secured using tie straps
  • Can allow minimal sunlight into the tank depending on the percentage shade you purchase. 70% shade works the best in this case.
  • Can allow air circulation in and out of the tank

Also depending on the shape of the tank you can use different materials. You just have to improvise a bit. See one of my fish tanks.

Since the tank was round. I used a similar water tank and cut off the top. I made a feeding port on one side with a flap to open and close and I also drilled holes all the way around to allow some light into the tank.

When using materials to cover the fish tank make sure not to properly seal the tank for obvious reasons. Remember it’s just to cover not to seal.

Do aquaponic fish need light?

Although fishes don’t need light to survive, I would recommend when using a cover over the tank ensure there is some light for the fishes. The light should not be direct sunlight to prevent issues previously discussed but more indirect sunlight.

This indirect sunlight allows the fishes to balance their sleep cycles just like humans. Light cycles contributes to the overall health and productivity of the fishes.
And as I always say, Happy fishes happy plants.


JayLea has a passion for plants and has been gardening since 2015. He has valuable knowledge about gardening and houseplant care and can answer everyday practical questions that every plant owner has.

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