Air System

 

The Blower

The best way to use a single pump for over 30 tanks is with a blower.  Linear compressor's are quieter, and better at pushing air deeper under water as they develop higher pressures, but max out at about 40 to 50 outlets depending on the exact model of the pump.  Blowers use an electric motor to spin a precisely balanced fan and pump much larger volumes of air but at much lower pressures.  I am using a 1/3 horsepower Sweetwater blower available from Aquatic Eco-Systems.  Currently it is operating about 150 outlets.

Piping

In order to maximize air flow it is necessary to use the right sized piping from the pump to the outlets.  As piping gets narrower the resistance goes up.  It is not a one to one increase but resistance goes up to the square of the diameter decrease.  The Sweetwater air pump came with  a pipe size chart based on number of outlets and length of run.  I tried to keep the sizes at the upper limits of their recommendations.  From the pump to each row of tanks, 6 rows of 12 tanks, and 3 rows of 9tanks, I used 1 1/2 inch PVC.  Along the 9 rows of tanks I used 1 inch PVC with the brass air valves threaded into them.  A length of 1 inch PVC also brings air outside of the main hatchery room where approximately 50 outlets are also in use feeding the fry and pre-dime size tanks.  This length of PVC probably should have been a little wider, but it only started out feeding 4 125 gallon tanks and was only half as long.  (The problems of expansion :)

Drip Emitters

When running multiple air outlets, especially if coming close to the capacity of the pump, minor changes in one outlet can change the flow to others.  Pulling a filter out of the water may stop the airflow to several other filters as more air is able to go through the line out of water due to decreased head pressure.  As airstones clog, valves need to be intermittently adjusted to maintain the proper airflow.  One way to balance the system and avoid frequent adjustments is by the use of irrigation drip emitters between the valve and filter or airstone.  After selecting the right sized emitter the valve can be opened fully and air flow will remain constant until the line totally clogs :)  You may need to experiment with different sizes of emitters for your particular application based on air pump, tubing size etc.  I use 1 gph emitters on standard sponge filters and 2 gph emitters on 1 1/2 inch airstones.  They also come in 1/2 gph and 3.3 gph as well as adjustable varieties.  You should order the button style, pressure compensating type.  They typically cost about 25 cents each.  I get mine from The Drip Store.

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