Reef Notes: When Clowns Attack!

Q. My 4-foot reef tank contains two green chromis, a bicolor angel, a flame angel, a yellow tang, a scarlet hawkfish, a royal gramma and two common clownfish. The problem is with one of our clownfish.

Every time I put my hand in the tank to clean it — that clownfish bites me. One clownfish is black and white, and the other one is orange and white. It is the orange one that is the problem.

Our clownfish are not aggressive to one another, just me. It is progressively getting worse. Now, two people have to clean the tank — one just to distract the clownfish. Is there anything we can do? The whole situation is driving us mad.
-- Geoff Luker

A. Obviously, you taste pretty good to this fish. I know your pain! Why is it that they always pick that tender bit of tissue between your thumb and forefinger? And how do they know to keep hitting the same spot? Or does yours prefer knuckles? Martin Moe Jr. describes a very funny scene regarding such a situation with a large, toothy tomato clown. The motion of pulling his hand out of the tank sent the fish flying across the room.

These little damselfish are surprisingly aggressive sometimes. Usually the presence of other fish reduces their aggression, but as your experience shows, this is not always the case with these fish.

Basically, it doesn’t like it when you mess around in its space. I can’t say for sure why clownfish become more aggressive, but it may have something to do with protecting a spawning territory. Usually the larger female clownfish are the ones that bite. I have sometimes seen biters suddenly stop their demonic need to shred my hands. I can’t explain why.

I have also seen clownfish sometimes become enraged at my decision to redecorate the tank when corals have grown and need to be moved around. It is an amazing thing to see a 2-inch-long clownfish vigorously push over a rock or coral that is much bigger than itself.

You asked what to do, and, frankly, I don’t have a definitive solution. For controlling barking in dogs there are behavior-modifying collars that give them a slight electric jolt when they bark. No such alternatives are available for bad behavior in fish, and I’m not even addressing the issues of cruelty to animals. It appears that you have to develop a thicker skin. If you can, try doing work on your aquarium after the fish have gone to sleep. You will have a few minutes of groggy time when the clownfish won’t bite you. But once it wakes up, you’ll have to stop or risk getting bit.

A. There are several ways around it. First of all, if you are available in the evenings to collect the larvae, it is a simple matter to be prepared to harvest them when they hatch. It is a much more complicated matter to actually succeed in doing this!
They hatch within two hours after the lights go off, or at least that’s when they are supposed to hatch. You can tell what day they are going to hatch by their appearance during the day. On the day before the hatch and the hatching day they have distinctly shiny, metallic-looking eyes.

To harvest them simply turn off the circulating pump temporarily just when the lights turn off. It is a good idea to start the dark period a little early on the night of the hatch, to encourage the eggs to hatch earlier, so you can go to bed earlier, too.

After they have hatched, if the room is dark and you illuminate a corner of the tank with a flashlight, the larvae will gather around the illuminated area and it is a simple matter to scoop or siphon the larvae out and place them in a larval-rearing tank. If you illuminate the tank before the eggs hatch, however, it may delay hatching so that you have to wait and wait and wait (yawn). In that case they will not hatch until you have left the room and gone to bed, and you can’t even try to fool them.

A more passive approach is to let the overflow do the work for you. If you have no mechanical filter associated with the overflow, and the drain pipe conducts the water directly into a sump, you can have it feed into a larvae collector made from a mesh-walled framed box (a large version of the type used for separating fry in freshwater tanks). The water flows out through the mesh, but the larvae stay in the collector.

You can also rig up a sump design that will retain larvae, if the water flows out of their chamber through a filter sponge with a broad surface area. This would only work if the sump was large and the flow through not so great as to suck the larvae into the sponge. In either case, the sponge or the mesh should be in place only when the larvae are being collected. Otherwise they would become clogged within a few days.

I have seen a setup where the larvae drained from the display tank into refugium tanks that had a perforated baffle on one end, which had a low velocity of flow through that prevented the fish from getting filtered out.

Lastly, if the eggs are laid on a rock that can easily be moved, it is possible to put the nest in the larval-rearing tank the day of the hatch. This is by far the best arrangement. Be sure to have an even rolling current over them, something you can set up with a wand-style airstone. You can find more detailed descriptions of these things in the books listed at the end of the column.

Frogspawn Coral
Q. Could you tell me what is the matter with my frogspawn coral? It has had these bubble membranes for about four months. They increase and decrease periodically. There are three sections (columns). The third grew after it was acquired. Only the two originals have the bubbles.
P.S. — I have moved it higher in the tank, but no changes have been observed.
— Larry Adams

A. The bubble formation in the Euphyllia is very interesting. I have seen it before in this coral and in many other corals. I showed some slides and discussed it in a lecture many years ago, under the topic of asexual reproduction in corals.

While it is not widely recognized as such, the net result of this bubble formation is the generation of new daughter colonies. If you are patient and don’t disturb them, and you maintain adequate calcium and alkalinity levels, a skeleton will form that will weight the bubble down and gradually separate it from the parent colony.

While the formation of “satellites” is well known in Goniopora stokesi, the bubble formation you are witnessing is a little different and not well described in the scientific literature. Although there are a few articles discussing it in the aquarium literature.

I have a suspicion that it may be produced by a virus, with a positive and benign effect on the coral. The reason I suspect a virus is that I have seen it “travel” in aquariums, affecting one coral, then another and so on.

Moonlights
Q. I added blue moonlights to my setup. How often should they be on? Every night or one week a month?
— Larry Adams

A. Regarding the moonlights, there is no “rule.” Their utility is mainly as a spawning cue for both fish and invertebrates in aquaria.

If you are really trying to simulate the lunar cycle, your options include connecting the light to a computer-controlled timer that adjust the intensity and photoperiod to match the lunar cycle (these do actually exist).

You can wing it and have it on every night, modifying the photoperiod with an appliance timer. The intensity of the moonlight can also be modified if it is a dimmable lamp.