Dropsy
Q. I had a goldfish that got dropsy, which I diagnosed by comparing its symptoms to those described in a couple of goldfish books I have.

My fish resembled a pine cone and just sat on the bottom of the tank. The outlook in the books was grim and my fish eventually died.

I put the sick fish in a separate tank, because I have two other fantail goldfish that are (thank goodness) still alive and healthy. I’ve stepped up water changes and general water care so this doesn’t happen again.

Anyway, in my books, it mentioned that “humane euthanization” was best if a fish contracted dropsy, but it didn’t say how to “humanely euthanize” a fish. If this should happen again, what are your suggestions?

I also have a question about Plecostomus cats. I don’t currently have any, and I don’t think they would do well in my little goldfish tank. Is all algae good for plecos to eat?
-- Karen Mehren
San Diego, Calif.

A. I’m sorry to hear about your goldfish. You have several options when euthanizing a fish:

• With your fish in a net placed on a hard surface, give it a quick blow to the head using a blunt object, such as a wooden dowel, broom handle, etc.

• Place your fish in a plastic bag containing water, seal the bag and place it in the freezer. As the water cools down and eventually freezes, the fish gradually goes to “sleep.”

• Place your fish in a bowl of water and drop in an Alka Seltzer tablet. The tablet gives off carbon dioxide and therefore decreases the partial pressure of oxygen, and the fish will gradually succumb.

• If you are not able to perform these tasks, ask your veterinarian to euthanize it for you.

No, plecos won’t eat all kinds of algae. In addition to any algae that may exist in a tank, supply plecos with sinking algae wafers, pieces of zucchini squash weighted to the bottom (remove the zucchini at the end of the day) and make sure there’s a piece of driftwood in the tank. There is some evidence that driftwood is important in the diet of plecos. Maintain excellent water quality as many species of plecos are sensitive to sudden changes in water conditions and to the build up of nitrogenous wastes.

Danios Don’t Dance
Q. I have a question about danio gestation and spawning. My 8- and 10-year-old boys have a 10-gallon tank that’s been up for about two years. Their tank has guppies, zebra danios and two little catfish.

The guppies reproduce fine. We have had two fat zebra danios for a number of weeks now, obviously female. I figure we could breed them and placed them in an in-tank breeding “cup/tank” (this worked for the guppies) for almost two weeks.

Afterward, we moved them to a little hex tank. How long do they stay fat? Is a month (or more now) normal for them to stay heavy? Is there a way to induce them to release their eggs?

I have read what I could find on breeding — “prolific,” “easy to breed,” “no specific water parameters” — I assume we have two males (slimmer looking) with the females.

We have gravel and some artificial grass on the bottom, and an air stone provides water movement. There is no other filtration, because they looked so huge I figure they’d spawn at any minute. They are near a shaded east window, but one book suggested moving them into the sun. We tried that a few days ago for less than an hour and then it got cloudy and has stayed that way since.

The tank is not “long and shallow” as one book suggested. Is that necessary? Any suggestions would be greatly appreciated.
-- Harry Haley
Yorktown, Va.

A. It is quite possible that you don’t have females but large males. I have used one of two characteristics to differentiate males and females. Females are usually more plump (especially prior to spawning) than males, and the light horizontal stripes of males tend to take on a yellowish hue, while in females they are whiter.

The zebra danio is an easy egg layer to spawn as long as you follow a few simple steps. Start by conditioning the adults with a variety of live, frozen and flake foods to get them in top breeding condition. During this time, set up a 10-gallon spawning tank containing 6 inches of water, a small sponge filter and a heater (make sure the heating element is completely submerged).

In this tank you must create a false bottom to prevent the adults from eating the eggs. This false bottom can be produced by placing a layer of large mesh net inside the aquarium, or as I prefer, a layer of glass marbles on the bottom of the aquarium. With either method, the eggs are allowed to fall through the net or down through the layer of marbles, thus escaping cannibalism from the adults.

When the females appear nice and plump and water quality is similar between the display and spawning tanks, I transfer four to six specimens into the spawning tank (e.g., three males and two females) and let nature do its thing. If all goes well and eggs have been released, transfer the adults back to the display tank.

The eggs should hatch in approximately 48 hours, at which time they should be fed infusoria or liquid food formulas. I usually remove the marbles soon after the eggs hatch to eliminate the build up of uneaten food, unfertilized eggs, etc. Very gradually, I fill the tank up to its normal level with aged water and maintain excellent water quality. As the fry get larger I feed them newly hatched brine shrimp.

Reader Response:
I greatly appreciate your fast response; however, you really didn’t answer my question of how long a female stays “plump” carrying eggs.

Ours have been carrying loaded abdomens for weeks. I’m pretty sure I have two plump females. One of the supposed males is frequently pestering one of the females, so I believe this is a mated pair. The other possible male (perhaps past its prime) and female aren’t doing much relating.

Does a female need a male to induce release of eggs? I have only fed them normal flake food. Will live food speed up spawning? Are they waiting for optimum conditions of shallow water and long swimming lengths before they drop their eggs? Can they hold their eggs until conditions are right?

My experience with zebra danios is that if the conditions are right (e.g., water chemistry, diet, young specimens and well-conditioned compatible mates), they will spawn very readily. Yes, in part, females will need the presence of suitable mates to induce the release of eggs.

If eggs are not shed, eventually the eggs will be reabsorbed. If we assume that all conditions are good and you do in fact have females, there is the chance that they are egg bound. When females appear to be egg bound, try raising the water temperature a few degrees. If this has no affect, add approximately one tablespoon of Epsom salts per 10 gallons of water. This acts as a laxative and may assist the female.