Air System
The Air System
Filtering the aquariums in a fishroom and providing for a good rate of gas transfer (carbon dioxide out and oxygen in) between the water and the atmosphere are decisions that need to be made early in the planning of a fishroom. The most cost-efficient method of accomplishing both is to filter the tanks with air-driven filtering systems. That does not mean that other means of filtering a tank will not be used. Power filters, cannister filters and powerheads all have their specific advantages and uses, but in my fishroom the majority of the tanks are filtered with sponge filters.
There are three choices for setting up a fishroom with an air system. You can purchase a lot of small diaphragm air pumps that can power only a few airstones at a time. This has the advantage that if an air pump quits only a few tanks get shut off. The disadvantages are higher equipment costs and higher energy usage. If a fishroom only has a few tanks, or only uses a few airstones, the use of multiple small pumps is probably the way to go.
The choice for large fishrooms, retailers and wholesalers is to install a system driven by a regenerative blower. A blower pushes a large volume of air. A small 1/4 horse power blower is large enough to run an average size fish store, but is usually too large for the average in-home fishroom. Unused air is allowed to bleed from the system in order to prevent back pressure on the blower. This wasted air means wasted electricity, and therefore wasted money.
The last option is to use a linear piston air pump. These are large pumps designed to create a lot of air pressure. Unlike a regenerative blower, back pressure is not a problem for a linear piston air pump (within reason). These pumps vary in size, capability and cost. The greater the wattage of the pump, the greater the number of high-flow airstones the pump can operate and the greater the expense. Here is the linear piston air pump I purchased from Jehm Co.
This is an 80-watt air pump that is advertised to power 60-80 airstones. If the air circuit is small and the tanks are shallow the pump can exceed those expectations. I did not anticipate needing to run more than 60 airstones in my fishroom, so a large pump would have been overkill. However, I currently run 92 (as of January, 2008), but there has not been any noticeable loss of proessure. I do want to replace this pump with a 120 watt unit and use this 80 watt as a back up.
A linear piston air pump is more energy efficient that a blower or several diaphragm air pumps. The best feature of a linear piston air pump, however, is that it is extremely quiet. Fish geeks come into my fishroom and one of the first things they comment on is how quiet the room is. Most people assume I have piped in air from a blower placed in another part of the house. The other factor in keeping the fishroom quiet is to use airstones. Small bubbles push water as well as big bubbles do (probably better), and are a lot quieter.
When installing the air plumbing, think about loops. Air pressure is maintained evenly in a system that does not have any dead ends. My room has a large bisected loop. The loop goes completely around the room and a pipe runs across the center of the room connecting opposite sides of the loop. I used 3/4″ pvc for the plumbing. This is another area of savings over a regenerative blower, which uses 2.5″ pvc adn fittings. The cost difference between plumbing the air with 3/4″ vs/ 2.5″ PVC is significant.
When you are getting ready to build your air system buy a bunch of fittings of various types. You will be amazed at what you will need to use. Here is my collection of fittings before I started.
The clear vinyl hose in the picture comes in very handy. My fishroom has many odd angles and obstacles that needed to be circumnavigated by the plumbing. PVC does not bend well, but vinyl tubing does. I used a male adapter fitting and screwed the fitting into the vinyl tube, then used a hose clamp to seal the tubing to the fitting. The other end of the fitting slips onto the PVC. The image above of the hooked-up air pump shows this vinyl tubing in action. Here are some more pictures.
Getting the loop around the stairwell:
Creating a gradual curve and accomodating the need for a tee juction:
I also installed a bleed valve in the loop to releive back pressure if I need to. This valve can also be used to prevent a back siphon event by eliminating negative pressure when the pump is turned off. This is a tee fitting with the tee being a female threaded fitting. I have a threaded cap that screws into the tee. By loosening the cap I can bleed air out of the loop. The bleed valve is located on the loop near the pump. When I maintenance the pump (change the air filter), I unplug the pump then open the bleed valve. When I restart the pump I plug it in, then tighten the bleed valve. This prevents a sudden burst of pressure hitting the loop.
Other than the flexible connections and the bleed valve, the rest of the loop is straight 3/4″ pvc connected with standard fittings. I did not glue my fittings. They fit very snugly without glue, I have no leaks, and if I ever want to rearrange the loop (or have to move.. uhg!) I can dismantle the system and reuse the parts. The loop is positioned above the highest tank top to prevent any back siphoning accidents.
The air valves that I use are the nickel plated lever style valves with a threaded back end. Installing the valves requires that a hole be drilled in the pvc, and then a thread tap be used to make threads in the edge of the hole to accept the threads of the valve. I used thread tape of the valve threads rather that silicone sealant. I am not interested in gluing things together if at all possible. I learned the hard way that if the tap is inserted the full length of the tap into the hole, the hole becomes too big for the valve threads. It works best if the thread tap is only put in half way. I tend to group my valves is sets. That makes it easier to find the one I want to adjust without having to constantly move my ladder. Another thing that I learned, the hard way, is that it is best is the valves are inserted so that they point down or at a steep angle. This will keep the airline from the valve to the tank from kinking.
