Q. We are new subscribers to AFI. My husband maintains a 180-gallon (680-liter) saltwater reef setup, and I have a 210-gallon (795-liter) indoor pond. I was thrilled to see a special section in AFI devoted to ponds, so I decided to take advantage of it and ask a question.

I cannot seem to keep water plants thriving in my pond setup. I have tried water hyacinths, water lettuce, two types of water lilies, a marsh marigold, water clover, floating heart, parrot's feather, water poppy, variegated sweetflag and some submerged plants. Some last several months before dying off, and others simply rot away. The one plant that has flourished is an umbrella plant. Despite the natural illumination, I think the problem could still be insufficient light.

Our indoor pond is situated in a room surrounded by glass, and it receives lots of natural sunlight. Right now there are two ordinary goldfish, one white fantail, two shubunkins and one lionhead in the pond. I maintain the pH around 7.2 and the water temperature about 70 degrees Fahrenheit (21 degrees Celsius). Ammonia and nitrite levels are unmeasurable.

I have a natural filtration system using different sizes of gravel in a bog setup. I am not happy with the look of the system and wonder if you have any suggestions for a substitute.

A. The natural filtration system you use is very similar to the filtration system I use in my sunroom pond. A box containing lava rock sits above the pond with houseplants growing out of it. The system has been operating for more than six years and has not required even a cleaning in all that time. The plants thrive.

The variety of plants you are having trouble with suggests that several problems may be occurring simultaneously. Generally my first guess whenever there are pond/bog plant problems is always insufficient sunlight. Most of the plants you mentioned really require a minimum of four to six hours of continuous direct sunlight daily just to stay alive. For them to really thrive, six hours is essential.

If the room does not allow this amount of sunlight to reach the plants, an alternative is — of course — artificial lighting. For this to be effective you would have to provide about 1000 footcandles at the leaf surfaces of each plant. The only way to do this is with racks of special plant lights located just a couple of feet above the plants. (Anyone who hopes that a few 150-watt spotlights tucked into ceiling fixtures 15 feet up will keep the plants growing is going to be disappointed.) I will tell you right now that this looks incredibly ugly. Moreover, it uses a very large amount of electrical energy.

Instead, you might try switching to shade-loving houseplants. Ferns, ivies, monstera, pathos and philodendrons work well. The plants should be potted like any houseplant and allowed to droop over the gravel box. Many of these can be planted in open wire baskets — especially ferns — and just set on top of the gravel bed, not submerged in the water. They will quickly send out aerial roots and runners through the wire that will wind through the gravel bed.

This approach will also remedy a second problem that might be affecting your plants — waterlogging. Yes, I know it sounds crazy to talk about waterlogged bog plants, but that is precisely the cause of rot. Bog soil has a natural porosity that allows oxygen to reach the plant roots. If you use the wrong soil mix with bog plants — and especially if you use a regular potting mix — your plants will rot away.

Bog plants and water lilies also rot if the crown is planted in soil. You can usually locate the soil line on a plant stem by simple visual examination. Make sure that the soil does not come above this line when replanting.

Of course, this could not have been the problem with the floating plants: water hyacinth and water lettuce. Here the problem could have been insufficient light, not enough nutrients in the water or water temperatures that were too low. Intense and continuous sunlight for six hours each day is important for these plants. The water must have a good nutrient base; you may need to add a good pond plant fertilizer. Both of these plants like very warm water and air temperatures — usually around 75 degrees Fahrenheit (24 degrees Celsius) or higher. If the temperature drops much below this level, the plants go dormant and die back.

Some ideas for sprucing up the look of your indoor pond filter were mentioned in my "Indoor Aquatic Ponds" article in the November 1991 issue of AFI. I can think of two immediate possibilities for your setup. Both of these retain the approach you have now — combining biological filtration with plants. On the one hand, you can break up the floor directly behind your pond and sink a gravel filter there. This amounts to simply taking what you already have and sinking it into the floor to match the pond.

Alternatively, you could build a nice plant stand/filter box combination that matches the wood and tile in the room. This could also be located behind the pond. Water could return to the pond by hidden plumbing, waterfall or stream.

No Nets for Koi
Q. We have just installed a small outdoor pond — approximately 400 gallons (1500 liters) in volume and about 14 inches (36 centimeters) deep. We keep three very lovely koi in it. We plan to take our fish in for the winter because the pond will certainly freeze solid over the winter. Our question has to do with netting and moving the fish. What is the safest way to do this? I have heard that the moving process can be especially harmful to the fish.

A. Netting and moving koi and large goldfish can be very harmful to the animals if done carelessly or incorrectly. Many pond fish become very large in size and weight. Their bodies are meant to be suspended in water. If they are lifted up in a net and bounced around, severe physical injury could result.

Especially damaging with rough handling is the removal of the protective outer slime coat, which acts as an outer skin. Anytime the fish brushes against something slime is removed. In the process of netting the fish, this effect can be so extensive that the fish become vulnerable to infection and parasites.

Netting and moving can also produce internal physiological responses that weaken the animal's immune system. This "stress" response can produce serious health problems days and weeks later. So, you are quite right to be concerned about proper procedure.

First, I strongly recommend that you use only shallow nets. There are a number of these that are marketed specifically for koi. The deep pocket nets sold in bait and tackle shops can seriously injure your fish. Given the price of good-quality koi these days, the price of a net is cheap — about $100.

Second, moving koi and goldfish with a net should be thought of more as corralling or herding. Slide the net below the fish, holding it parallel to the water surface. Keeping the net rim just above the fish's eye level, guide the fish through the water. Again, do not try to lift the fish. Do not be surprised if the fish jumps the net rim.

Third, actual moving of the fish is done with a pail, pan or bucket. I prefer the large Rubbermaid-brand rectangular pails for this chore. The sides are high and the fish cannot leap out. Plus these pails have strong handles and the lids snap into place. These pails are available at most discount stores.

Partially submerge the pail in the pond and herd the fish into the pail. Once the fish is in the pail turn it right-side up. Pour out just enough water so that the fish's dorsal fin remains submerged. Carry the animal to its destination, submerge the pail and tilt it so that the fish can swim out.

Studies have shown that you can decrease transport-induced health problems if you add salt to the destination pond or tank. The concentration should be about 1 gram of salt per liter of water. This is roughly equivalent to 1 pound (0.45 kilogram) of salt per 100 gallons (379 liters) of water. Maintain this level of salt for a week or so, and then you can begin to dilute it with water changes.

A second way to reduce stress is to use water from the original pond in the destination pond. That is, whenever possible, the destination pond should contain water removed from the origination pond. This way the fish do not need to adapt to new water chemistry. Then, over a period of days, partial water changes can be used to freshen the destination pond water.