Backyard Aquaponics
A place to discuss aquaponics

Greetings,

I have noticed that the water turns green every week. I have 13 tilapia fish in a 500-gallon water tank. I have covered it, so it's not exposed to the sunshine. I have attached some photos to provide a better perception.
Is there any filter that would clean the green water and turn it pure? My understanding is that there is no harm to the fish. But I would love to watch them with the kids, and having green water does not allow us to see them! Pumping the water to the plants on a weekly bases is not convenient.

I have been told that the attache filter but was not sure if it is the right one or not, and your advice on resolving this issue if highlight appreciated.

Thanks in advance,

Hi there.

My pond went green during spring time, we also wanted to see the fish better etc, so we built an experimental static upflow sand filter. It wasn't a success, but it did have an effect and could probably work better if the design was improved...

basically, you need to pass water slowly in an upward direction through fine sand. The sand must be static, if you can see it moving around on the surface then the water is taking a shortcut and its not filtering, the flow rate must be reduced.

when we observed the water coming out of the filter, it was very slightly cleaner than the pond water. When we cleaned the filter out by washing the sand by sticking a hose in it, the water came out very very green, so obviously it was somewhat effective at trapping the green.

Having said this, the overall effect on the visibility in the pond was negligible. The pond is crystal clear now though, and this is basically since we introduced pond lillies.

If you have the time and energy, and access to lots of fine sand for free (live near a sandy beach), and a spare small aquarium pump and large container then you could give it a try.

I would use a 200 litre drum if you can; distribute the inflow at the base of the vessel through a perforated pipe, and have the outflow at the top, above the level of the sand.

Its obviously a lot of sand though, and might not be worth it... It should go clear anyway, with time if the water is not in the sunlight.

An alternative faster and more interesting option would be to introduce freshwater bivalves if you can get hold of any in your area. Beware though, some (or all?) freshwater mussels of the unionidae family are parasitic to the fish when they reproduce!

In my limited experience, white tanks allow in enough light to allow algae growth, which turns the water green. I have had good luck wrapping the white tank in tarps, burlap, or reflective insulation to block direct sunlight.