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  Plant Filters

Goliad Farms exclusively uses plant filtration designed by us. We have no carbon or mechanical filters.

Our plant filters in our two large greenhouses (about 3,000 square feet each) consist of three main stages. Our smaller greenhouse (about 1,500 square feet) uses the plant filter in one of the two larger greenhouses. Below is a description of the two large greenhouse plant filtration systems.

First Stage: The first filtration stage uses plants in the vats. Our plant of choice for this stage is hornwort (Ceratophyllum demersum), a rootless floating plant that we stock in most of our vats. This is a rapidly growing plant that does not suffer a significant slow down in growth during the winter. We keep a ten to twenty inch sprig with new growing tips in each vat. About once a week, the sprig is pulled out and the older end pruned and discarded. In addition to the hornwort, there is a group of volunteer plants often present in the vats. The group includes several species of algae (mat and hair algae primarily) and duckweed (Lemna). We don't encourage these plants, especially the duckweed, because it interferes with feeding and netting, but they are present and almost impossible to eradicate. These plants heavily on the ammonia waste products of the fish.

Second Stage: The second filtration stage is a complex of plants in our floor gutter. This complex consists of hornwort, algae, Bacopa and duckweed. Again the algae and duckweed are volunteers that we don't particularly encourage but tolerate out of necessity. Bacopa is a native plant with an emersed growth pattern. It forms floating mats and grows up on to our wooden walkways. Its primary deficit is a tendency to go into dormancy in the winter and ceasing to grow. The floor gutter is thirty by eighty feet in area and averages six inches deep. It is walled on three sides and is dammed at the open end by a thirty foot long, six inch high wall. The water falls over this wall into the plant filter. The gentle flow of water causes mulm and detritus collect in front of this wall. Periodically, we remove the collected detritus with fine meshed nets.

Third Stage: Third and final stage of filtration is a sump at one end of each greenhouse. This sump is about thirty by seven feet in area and several feet deep. The sump is populated with Red Mangroves. Mangroves produce thick, fleshy leaves that require heavy feeding by the plant on the fish wastes in the system.

Collectively, the three stages of plant filtration maintain zero levels of ammonia, nitrate, and nitrate in the system. We continue to experiment with new plants such as black mangroves and black willow.

Page last modified January 1, 2010.
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