Drip plates should do just that: drip. Or better, make the water coming down from the aquarium drip evenly over the biological medium, spreading it out as much as possible, breaking it up in small streams, and wetting as much of the medium used as possible. Any medium that is not wetted is not used, and is, basically, a waste of your money. Although spray bars break up the water very efficiently, they have the unfortunate quirk of slowing down and stopping.

The reason is simple: dirt, detritus, algal debris, and so on, slowly move into the area that assures the rotation and hinder the free spinning of the bar that distributes the water. When this happens water is distributed very unevenly and only on a small portion on the biological medium. This is a very inefficient use of the medium, and reduces the overall efficiency of the filter greatly. Look at it in this fashion: if you used the medium more efficiently you would need less of it because more of its surface area would be populated with Nitrobacter and Nitrosomonas bacteria.

Many different designs have been tried to make spray bars more efficient, and many different materials have been used to make them rotate more smoothly and for longer times. Rulon, Viton, polypropylene, polyethylene and other such noble materials have all been given the test. No one has convinced me, yet, that their model using a specific material will work as long and as well as drip plates do.

Drip plates are relatively easy to make yourself, or to modify if need be. Whether or not this needs to be done depends on the kind of filter you own, or plan to acquire. Several features need to be examined:

• the size of the holes,
• whether they are tapered or not,
• the spacing of the holes,
• how far from the edges they start,
• whether they are staggered or in-line.

Here is a simple procedure to make an efficient drip plate, or modify the one you have:

• Carefully measure the inside of the filter's biological chamber.
• Buy a piece of ¼ inch acrylic of the exact above dimensions.
• Scribe lines in one direction, using a sharp tool or a plastics scriber, and make them 1 inch apart.
• Now draw lines 1 inch apart, at a 90 degree angle with the first set of lines.
• Do not draw lines within approximately 1-1/2 inches of the edges of the plate. This will prevent water from channeling along the sides of the chamber.
• Where the two sets of lines intersect drill a 3/16 inch hole (this could be quite a few holes especially in larger filters.
• After you have drilled the holes, use a taper bit and taper the holes to ensure a better downward flow.

Note: it is not necessary to groove the lines that you draw in both directions. The reason that you use a scribe (that makes a fine scratch in the plastic), is to determine the intersection points and make it easier for you to know where to drill the holes. The drawing shows both the initial step, and the end result. For more flow, space the lines ¾" apart.

When placing the drip plate inside the filter, a fine bead of silicone aquarium glue can be run around all the edges to seal the drip plate down, and prevent water from escaping along the sides and running downwards along the inside plates (channeling). This may not be necessary in all cases. Such will depend on how tight a fit the plate really has to the biological chamber. Should it become essential to remove the plate to perform some work on the inside of the chamber, all you will need to do to remove the silicone bead, is to cut it in one spot with a razor blade, and then by lifting it up and pulling it off the plastic, remove it from all around the drip plate. When resealing the plate keep in mind that silicone adhesive does not stick to wet plastic.

As water flows down from the tank and enters the trickle filter, at the top, it hits the drip plate and spreads out, covering the whole drip plate before flowing onwards through the holes in the drip plate, and onto the biological medium. Usually, in a system that is well-balanced, the flow will be such that a shallow layer of water will always be present on top of the drip plate. Since all holes are covered with water, the air that you are blowing into the biological filtration chamber from below has no where to go. This builds up internal pressure, inside the biological chamber, and this pressure must be released, otherwise the top of the filter may overflow. The latter would only happen if the water in the sump was also high, and prevented air from escaping through the bottom. An air lock would occur and the filter would overflow. Although the situation is not common, it is a possible scenario, and measures to avoid it are easy to incorporate in the filter's design, and can be seen in the drawing.

Some hobbyists who use carbon dioxide on their systems wish to be able to minimize gas losses. To this effect they run a small piece of tubing from the top of the filter (the pressure release area), to the sump, and submerse that piece of hose. As pressure builds up inside the chamber, the gasses travel down the tubing and bubble back into the water of the sump. Some CO2 is saved in that fashion, but I have not been able to find any references to the amount or the efficiency of such a system in the long run. You should be aware, nevertheless, that it is a possible scenario, and how to deal with it. Whether you want to use it yourself, is another matter altogether.

If your filter now has a spray bar, and if it does not function properly for any length of time, you may want to consider changing to a drip plate, or if such is not feasible, you may want to buy a better spray bar. Several types are advertised in magazines such as _FAMA (Freshwater and Marine Aquarium)_, Marine Fish Monthly, and _TFH (Tropical Fish Hobbyist_).

Companies such as Marine Technical Concepts and Route 4 Marine Technology, sell spray bars made of more durable and smoother materials. Check with them for more information on their latest products.

Drip plates used in systems that have lots of macro-algae, and perhaps not as good a pre-filter as they should, need cleaning from time to time, to ensure even distribution of the water over the medium in the chamber underneath. Several methods to unplug holes, or clean holes exist:

• use a small piece of electric wire and push it through the holes,
• use a pipe cleaner and push it through the holes,
• in the case of Platinum filters, remove the pre-filter drawer at the top of the biological chamber, and clean it in your sink with a brush.

Do not use soap, or any similar material that may leach into the water afterwards, and affect the animals in the aquarium. Plain water and a brush that has not been used with soap before should do. If, however, the water that enters the biological chamber has been pre-filtered well, you should have no problems keeping the drip plate clean and the holes open. Checking it from time to time certainly cannot hurt, and can be made part of your regular maintenance schedule. A suggested schedule is listed towards the end of the book, and covers all aspects of the aquarium.

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