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Aquaponics Fish Growth Using an AST Bead Filter System

A Guide To Growing Fish In An AST Bead Filter System
Photo by Sebastian Pena Lambarri

Key Information:

Aquaponics Fish Growth Journey, using an 260-gallon AST MDC 1000 system. AST Site

50 fish take roughly 6 months (190 plus/minus 10-20 days) to grow to full size of 1 pound.

Use feeding charts at 


Young Fish:

Young fish should be grown in a small tank (a medium-sized fish tank for pet fish will work) until they are large enough to avoid being sucked into the filter of the main tank. 

This stage takes about 2 months. 

An automatic feeder can be installed to feed the fish when nobody is present. 

An algae bloom is possible. If conventional filters are unable to handle it, a UV sterilizer should be installed to kill off the algae. 

During this phase, DO NOT directly add tap water to the tank. Instead, leave the tap water in a container (bucket) for 2-3 days to “air out” any chlorine or other chemicals and make the water safe for the fish. 

If raising the fish for human consumption, DO NOT add any substances for any purposes to the water or food unless confirmed that such substances are safe for use on fish intended for human consumption. 

Test the water frequently (Once per week at least) to ensure healthy levels of tested substances. Additionally, before moving fish to the larger tank, ensure the water in both the small and large tanks have similar levels of the tested substances. 

Water Testing Areas (Good, but not limited to):

  • Ph (Acidity)
  • Dissolved Oxygen
  • Ammonia
  • Nitrate
  • Nitrite
  • Phosphate


Juvenile Fish:

Move the fish into the large tank when the smaller tank is becoming “cramped”, and the fish will not be sucked into the filter in the larger tank. These conditions are up to the operator to decide. 

The AST 260 gallon 1-tank Bead Filter System has:

  • Two white blocks made of a porous material, which, when the air pump is turned on, release oxygen underwater, giving the fish oxygen to breathe. 
  • The filter is linked to a smaller tank, which is where the “sludge” produced by the filter is sent. It is advised to put a cap on it as the odor is very disagreeable. The sludge tank should be emptied before it is full, either through the discharge valve, or by detaching the tank and dumping it in whole. The sludge is produced in large bouts when the filter is in its backwash phase. 

Ensure the water is heated to between 75-85 degrees Fahrenheit. 

NEVER drain the water in the tank to below ¾ – ⅔ of its volume, or else lack of pressure will compromise the filter and air pump systems. Lack of oxygen is the quickest way of killing the fish. 

If possible, it is advisable to have a place to store a large amount of water nearby so the water can air out. If the tank gets dirty for whatever reasons, large amounts of water can be quickly replaced without compromising the water level or the water quality.

If unsure about the proper feeding amount:

  1. Catch a fish (the easiest way is to take a large net, run it over the bottom of the tank and up all the sides, and pulling up)
  2. Weigh it
  3. Calculate total weight of all fish from weight of one fish and the estimated number of fish in the tank
  4. Use the provided feeding charts to find the proper weight of food per day.
  5. Adjust the automatic feeder (if it exists) to feed the proper amount. 

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