Q. I own oranda goldfish that have nicely developed hoods. I am concerned about one of them. When I purchased this fish it had a red spot on its head. I did nothing about it and soon there were more. The spots seemed to move around like parasites. Sometimes white cotton-like tufts would appear. I have treated the fish with Mardel's Maracide and Maracyn-II. I followed the instructions and the fish seemed to get better. Two weeks later, however, the red spot appeared on his head again. How can I treat this fish?

A. Fish medicine is a difficult business for professionals and it is downright frustrating for hobbyists. First, you have to determine what the problem is. Is it water quality, something in the physical environment, a perfectly natural event (yes, many hobbyists misdiagnose normal behavior as a disease), bacteria or parasites?

Once you have settled on a class of problems, say parasites, you have to figure out the general type of parasite. Is it one of the larger types, a microscopic parasite, a fluke, a ciliate? It does matter because there are no universal cures.

Then, given that you guessed correctly, you have to find a remedy. The search for a good "cure" is complicated by the diversity of putative fish medications available on the market. Unfortunately, the majority of these products are of little or no value. Only a handful have ever been approved for use on fish, and an even smaller number are sold in concentrations that have any therapeutic effect.

In your case, I think you actually made two good guesses. Mobile red spots frequently indicate that external parasites are munching on your fish. The red spots are irritation points. Usually any parasite that can raise visible red spots is large enough to be seen through a magnifying glass. So, the first step I would take in your case is to place the fish in a small bowl of pond water. Use just enough water to keep the fish afloat; this is usually just to the base of the dorsal fin.

Do you see any critters scurrying about or dug into the fish? Large parasites, such as anchorworm and fish lice, which can be seen with the naked eye, require physical removal and treatment with a trichlorfon-based chemical, such as Aquarium Products' Lifebearer.

If you cannot see any parasites the problem may be one of the microscopic species, such as Trichodina, Costia, etc. These parasites, however, generally produce a bluish-white film on the fish, although red spots may also accompany an infestation.

I find Mardel's Maracide a very useful aquarium medication for dealing with the latter type of external parasites. It is a buffered mixture of mercurochrome and malachite green. (Never use any fish drug that does not list its ingredients. If you want to throw away your money, just mail it to me in an envelope.) Had I detected Trichodina or a similar microscopic parasite, I would turn to this product.

(Your use of the Maracyn-II, though recommended on the Maracide box, was not called for. While this monocycline-based anti-bacterial can be used effectively, its use in your case was not necessary. As most regular readers of my AFI contributions know, I do not subscribe to the prophylactic [shotgun] use of fish medications — even those that work.)

In any case, assuming you followed the instructions on the Maracide bottle correctly, and assuming the problem was parasites that were treatable with this product, the red spots should not have returned. This suggests that the problem was not external parasites. Orandas and other "hooded" goldfish often develop these red spots marked with white cottony plumes on their heads. The poor blood flow to these hooded areas makes them prime targets for fungal infestations. The white tufts you observed are undoubtedly fungus. The red spots, then, are irritation points (there may also be some external bacterial activity).

In a healthy fish these minor nuisances are not a serious problem. Often, regular water changes will clear them up. Raising the water temperature above 70 degrees Fahrenheit (21 degrees Celsius) sometimes eliminates the problem. Alternatively, you might try a malachite green and formalin mixture. There are many commercial products available that use these ingredients in standard formulations. Pond quantities are available in Tetrapond's Desafin.

Clogged Screens
Q. I am having trouble with my pond filter system. The pump screening basket fills with debris too quickly. I have to clean it out once a day. I was considering removing the basket altogether, but a friend told me that this would leave the pump impeller unprotected and I might risk jamming the pump. Is there some way I can have good mechanical filtration that doesn't require daily maintenance?

A. Given the amount of physical debris you seem to be collecting in the pump strainer basket, it would indeed be risky to operate the pump without it. But I also agree that the daily maintenance routine gets tiring after a while.

Let me offer you a home-built alternative. This is a large-scale mechanical screening basin that only needs cleaning once a month. It traps everything from leaves to small fish to snails to larger algae. Total cost is about $35.

Basically, you go out to your local discount store and purchase a 32-gallon trash pail and two clothes hampers with grilled midsections. Make sure the hamper will fit easily inside the garbage pail. You also need to buy several feet of nylon mesh window screening and some duct tape.

Wrap the outside of one hamper with the window screening, covering the grill area. Use the duct tape to hold it in place. Now insert the wrapped hamper into the second hamper. The result is a giant strainer basket.

In the final setup, the trash pail becomes the outer basin and the combined hampers become the inner basin. Put a standard 1.5-inch bulkhead fitting through the wall of the trash pail about 12 to 15 inches down one side. This will be the outlet for the filtered water that leads to the pump.

There are two ways to set up the inlet, depending on your pond design. In the first way, water from the pond enters over the top of the basin and falls into the inner section (the hampers). The second way is to run a pipe through the outer basin wall and also through the inner basin wall below the water surface. This is more complicated but it may be necessary for some in-ground installations (this is the way I have mine set up).

I have found this setup to do a wonderful job of mechanical filtration. I especially appreciate it in the spring when it catches all the koi fry, and in the fall when it holds 20 gallons of fallen leaves.

Cleaning merely involves pulling out the inner basin and hosing it down. Total maintenance time: 10 minutes a month. Ahh...my kind of pondkeeping!