Continued from page 4

Converting and Removing the undergravel:

In the interest of maximizing water quality, it is much better, filtration-wise, when converting to a modern Reef System, to remove the undergravel filter completely. This may not be as practical as the previous solution, but it is definitely more efficient, and to the benefit of all tank lifeforms, especially the more sensitive corals and invertebrates.

Because of the nature of dolomite, or crushed coral, and the usual size in which it is sold as undergravel filter material, it easily traps detritus as water is pulled through it by the up-lift tubes and by, power heads. In fact more so with the latter.

Many Hobbyists will remark that reverse flow is a much better way of operating such filters, because the water can then easily be pre-filtered before it is pushed back through the filter bed itself, and into the aquarium. That is of course entirely correct, but detritus still gets trapped. It is just of a smaller size, and the clogging process will take longer to occur, but occur it will. Just stir up an old undergravel filter bed, and you will agree with me that the material that you can see coming out of the filter bed, cannot really be conducive to the higher water qualities that we are looking for in a Reef aquarium.

We are not saying that undergravel filters do not work, they do of course. If they did'nt, the hobby would not be where it is now. What we are saying is that you can do better, improve the water quality significantly, by removing the undergravel and switching over to a trickle filter as the sole biological filter of the tank.

The steps involved in doing this are similar to the ones described in the previous section, up to the point where we recommend that you clean half of the undergravel bed thorougly. Instead of waiting 7 to 10 days, wait 14 days, meaning let both the undergravel and the trickle filter run the tank for 2 weeks, then remove half of the undergravel (or in larger tanks remove one third) including the plates.

This is labor intensive work for which you must plan, as it may take quite a while to do. After the plate, the crushed coral and dolomite are removed, perform a 20 percent water change. Wait about 6 hours, then perform another 10 percent water change. Since you may have two (or more) plates to remove this whole process may take up to 30 days to complete. Change plates at 10 day intervals, and perform water changes each time, as indicated.

The easiest way to remove the dolomite, or crushed coral, is to syphon it out with a large diameter hose. This will reduce the amount of material (detritus and mulm) getting into the water. You will be removing water at the same time, which you need to do anyway, because of the recommended water changes. Watch the pH, and add a carbonate hardness generating fluid (or tablets, powders without binders), if it drops too low. Beware of products that contain nothing else but baking soda !

Remarks on the Conversion Process:

Because in both types of conversions the existing undergravel, and the new trickle filter, are running at the same time, the seeding of the new filter with bacteria is automatic, and the cycling happens without the Hobbyist noticing it. Indeed, you already had a lot of bacteria in the system. They are being transferred to a different medium.

As long as the existing undergravel filter was able to keep ammonia and nitrite down to zero, no increase will be noticed in the first 7-14 days, while both filters are running together.

After cleaning the undergravel (in one scenario) and removing part of it (in the other), a small amount of ammonia and nitrite may be present for a few days. The amount will, however, not be high and stress on the fish will be minimal. There will be some degree of stress that the animals will have to cope with, that is unavoidable, indeed, you are making changes.

Do not add any fish or invertebrates whatsoever during the conversion process! None whatsoever.

Clean all mechanical filters before you start the conversion.

To alleviate stress on the tank life change your Poly Filters if you are using them already. If you are not, we suggest that you add 1 Filter per 25 gallons of water in the system. To find that number, add the volume of water that is in the sump, to the gallon content of the tank. Multiply that by 90 percent (to account for displacement by rocks etc..) and use that number.

Remember that the water going to the trickle filter needs to be pre-filtered. If you don't do so, you will have to clean the drip plate of the filter regularly. Good quality syphon surface skimmers will have such a pre-filter built-in.

If you are using a spray bar, which we recommended you did'nt, pre-filtering is even more important.

The recommended water changes that go in hand with the cleaning of the undergravel filter, and removing the plates, are very important. They are meant to remove the noxious toxins that result from stirring up the material used on the filter plates, from the water. Not doing so may lead to a lot of problems.

In the first type of conversion, where the undergravel filter is not removed, you must clean the undergravel filtering medium very thoroughly, to remove any material that can cause oxygen depletion, anaerobic activity, plugging of the crushed coral or dolomite, etc.

In the second type of conversion, where the undergravel is removed in several stages (at least two), it is very important that the medium on the filter plates be syphoned out. This will prevent the detritus in the crushed coral, or dolomite, from mixing with the tank water. Some of it will, but you must try to minimize that mixing as much as possible, because of the toxins it also contains.

Remember not to turn the undergravel filtering system pumps (air or power heads) completely off. Reduce the throughput, but do not shut it off completely. If you do, the layer of water underneath the plates, and the material on the plates, will quickly produce anaerobic by-products. This may kill off everything you keep in the tank. Many Hobbyists have made that mistake before you, and have wondered why, even though they added a trickle filter, they could not raise the water quality.

Do not rush the conversion. Take your time. Follow the suggested timeframe. Your fish and invertebrates will benefit from it.

If you were using canister filters in conjunction with your undergravel filter, you can certainly continue to use them with the new filtration you installed. It seems, however, that they should then be used for other purposes : additional mechanical filtration (clean them at least once a week), chemical filtration (see next section), special compounds e.g. to remove nitrate from the water, etc.Run them, taking water from the sump, and returning it to the sump.

Because of the changes you are making to the filtration, initially, changes to the water chemistry will affect the redox potential; it will go down, but come back up after a few days, to a week maximum.

Dissolved oxygen and carbon dioxide levels will also be affected, but not to the point where you have to be concerned about it.

Changing over to trickle filtration is a positive move. It will take time to perform, but it will greatly benefit your system in the short, and long run. It definitely is a positive step for the water quality, and ultimately for how your tank will look some weeks down the road.

[Albert J. Thiel requests that you make a $5.00 donation to the New Mexico School for the Visually Handicapped Children, 1900 North White Sands, Alamagordo, New Mexico 88310 (or other charitable group) if you download the entire book. This would be in lieu of the standard purchase price for this publication.]

NetPets® Main Page

contact information Main Reference Library

The Fish Center