These fishes live in 'condominiums'

DAGUPAN CITY, Philippines – Some fishes here are “privileged”.

They live in “condominiums.” Fish condominiums, that is.

Home to them are actually multi-level chambers (drums) where one can commercially raise fish even in one’s backyard.

One condominium, said noted fisheries scientist and research administrator Dr. Westly Rosario, is composed of seven chambers or drums, arranged in three “floors” or layers.

Arranged at the first level are three drums while the second and third layers consist of two drums each.

Each drum is composed of two metal drums welded together.

The design optimizes utilization of electricity to filter and aerate the water. Filtration design is simple, cheap, effective, and practical, which allows continuous reuse of water.

The continuous flow and recycling of water, using 0.5 horsepower submersible pumps, serves as the unit’s life support system.

The fish condo is equipped with mechanical cum biological filters in the outlet piping system, a filter box on the topmost level (atop the third level) and a settling trough (basin) on the ground level (below the first level).

The basin collects solid waste and acts as catching trough before the water is pumped to the top level filter. Water pumped from the settling trough is subjected to another filtration before it is recirculated to the culture chambers.

A condominium has a floor area of 2.3 meters by 1.8 meters and a height of three meters, making it suitable even in densely populated areas such as cities, said Dr. Rosario.

Dr. Rosario, who is interim executive director of the Department of Agriculture-Bureau of Fisheries and Aquatic Resources-National Fisheries Research and Development Institute based on Bonuan Binloc, Dagupan City, developed the technology in 2001.

Since then, he has innovated on it, particularly the fish species to be raised in the condominium.

He had tried tilapia but found that the species depended much on oxygen. Thus, in case of a brownout, an oxygen supply problem arises.

Ulang (native freshwater shrimp) was also raised but this crustacean needs something to attach itself to limit its mobility but the drums do not have it.

Another species experimented on was silverperch (from Australia) but one can only raise them in limited number.

The latest to be tried was African catfish (hito), which has so far proved to be the most viable.

Fact is, Dr. Rosario explained, catfish has a special lung that can absorb oxygen from the atmosphere.

Initially, though, they have encountered one problem with catfish: it is cannibalistic, meaning, the bigger ones eat the smaller ones.

But this has been solved with NFRDI’s finding that it is best to stock catfish in the chambers when they are already the size of a cigaret. At this stage, cannibalism is no longer indulged in.

Dr. Rosario said 300 to 350 fingerlings can be stocked in one chamber.

“Catfish can grow in a fish condo to marketable size in four months,” he said.

He reported that in their latest harvest, a drum yielded 40 kilograms, or 280 kg for the whole culture period.

Another advantage of the technology is that the water used in raising the fish can be used in watering vegetables that can be grown just outside the condominium. The water from the condo is rich in nutrients.

It is expected that the fish condominium technology can serve as a touch-off to an “urban aquaculture revolution” that can help produce more food of fish origin in densely populated areas, particularly in cities where land is limited.

To date, Dr. Rosario reported, many people have been communicating with DA-BFAR-NFRDI requesting more information about the technology.