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Backyard RAS system

Basically, this let’s a fish farmer grow fish in a tank and reuse the water.




When in Baguio, this writer visited strawberry farms and an aquaponics greenhouse, and then made a detour to the residence of Alex Wilcosach, the administrator of a Facebook group called RAS Fish Farming Philippines.

RAS stands for “Recirculating Aquaculture System.” Basically, this let’s a fish farmer grow fish in a tank and reuse the water. This is done by removing fish waste solids (through filters) and then converting the toxic ammonia to nitrites (still toxic) and then to nitrates (generally not harmful to the fish) through the help of beneficial bacteria. This process is called biofiltration (or nitrification). The bacteria involved are identified as nitrifying bacteria.

As a background, Alex was an OFW and, having returned to the Philippines, chose to stay. He became interested in RAS around two years ago and kept researching about the topic. He then built his own backyard system.

He has two rectangular concrete tanks but only one is operational since the other one had leaks. He uses a submersible pump and a split flow system. Whenever the pump is turned on, water is carried out of the tank and then splits into two different flows. The first flow goes up to his roof and passes through a series of pipes before returning to the fish tank. It turns out that this is how he harvests the heat of the sun to warm the water in his RAS. While warming water may sound odd for those from Manila, it makes sense for people who live in Baguio where the temperature can be very cold.

Chopping board, PVC rings, epoxy and bulk head fitting equivalent in the making.

Best of all, Alex is able to heat his water without the need to use a heater thus saving on electricity costs. He is able to start the first flow — depending on need — through the use of valves. For example, if the temperature in Baguio isn’t cold, thus no need to heat the water, the valve is turned off. If it’s cold, and he needs to heat the water, the valve is turned on.

As for the second flow, it travels to an elevated portion of Alex’s residence where it goes through several blue drums that act as filters. The insides are filled with nets to capture the solids. Occasionally, these filters are cleaned. The water then travels back to the fish tank where the tilapias are growing. The entire cycle is repeated again.

Alex shows the different pumps that he has worked with during his backyard experiments.

One of the problems when it comes to pipes and fittings is how to slip a pipe through a tank or a drum without causing leaks. Uniseals or bulkhead fittings are used for this purpose. Interestingly, Alex found a way to fabricate his very own equivalents of bulkhead fittings.

There are three pieces, the first one is the bulkhead, then there’s a rubber gasket, and then there’s a nut which you screw on the bulkhead (the gasket is in between the bulkhead and the nut). You then attach male PVC fittings on both ends and can securely slip on PVC pipes. Alex fabricates his own version by using plastic chopping boards, cut out PVC rings and epoxy.

This filter separates the settleable solids from the water.

RAS, as an industry, is either very young or practically

non-existent in the Philippines because fishing is still done in ponds or floating cages. Alex’s system is still small, same with others — like this author’s — who are operating backyard setups. True, there’s still a long way to. But let’s not forget as an old commercial motto from the 1990s: “Great things start from small beginnings.”

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