I Used To Think The Fish Was Stupid

Well, not really, but it did appear that way.

I have a soft coral reef and there are only two fish, a Fijian blue damsel (Chrysiptera cyanea) and a flame angel (Centropyge loriculus). Under white and blue lights they both display stunning colour, and the damsel even more so with just the blue (actinic) lighting. The flame angel is the boss of the aquarium, the damsel getting out of the way when approached and also getting periodically chased a little just to let it know who the boss is.

Like other aquarists I sit and watch the aquarium and get a lot of pleasure from it. This usually occurs after feeding and it was at feeding and directly after that I vaguely wondered if the flame angel had less intelligence than the damsel. Seems a strange thing to consider but it was the fish feeding that brought it on.

Generally the fish are fed a de-frozen food such as mysis or brine shrimp once a day and marine flake once a day. One feed type will be in the evening and one in the morning with each type feed time varying. Sometimes I purposefully give a feed a miss.

Anyway, as soon as I approach the aquarium both fish appear at the front showing heightened interest, swimming along the front and also up and down. ‘Food’ they seem to cry, ‘and get on with it!’

In goes the food and like a flash the damsel is on it. Sometimes the fish darts around so fast the food is just gone. Wherever the food gets driven by the seawater currents, provided it can be seen, the damsel gets it. Of course, the point comes when it starts to lose interest.

The angel is much more sedate. It swims along and takes food well, without the speed of the damsel. However, it ignores food which is some distance away. At first I used to mutter ‘Stupid fish, eat it, the damsel’s getting it all.’ I wasn’t annoyed with the fish, only with the possibility that too much food could get into the rocks of the reef. I feed carefully, a small portion at a time until the fish show signs of loss of interest.

I used to note the damsel losing interest but felt some concern for the angel – had it had enough or should I feed some more? So when the damsel lost interest I used to generally target feed the angel, that is, wait until the angel was in position and drop a small amount. The angel would chase food to an extent once it had seen it. Generally the method worked, but it was a bit of an annoying requirement. Both fish were not overfed but displayed a good body shape.

It was after a feeding I decided that I was being unfair to the angel in wondering if it was stupid. The damsel took food nearly instantly from all over as long as it was in sight, and this was and is because that is how they feed on the wild reef. They hang in the water column awaiting food items, and if any are seen speed is required to get the food before others, and good distance eyesight is required to see the food in the first place. The flame angel goes along looking for food on rock faces and in crevices and caves, which is a much more considered affair without the need for speed. Also, the distance of potential food from the fish is short. The flame angel is an omnivore and if anything is floating about that is edible it will be eaten, but it is not the natural prime food location. So – my apologies to the angel.

I don’t target feed the angel anymore, this was only in the early life of the aquarium. The food is still fed carefully but if any drifts into the reef rockwork I’m not alarmed. Now that the aquarium, which is over six years old, has developed I’m aware that there are a large number of tiny life forms about. I have only to look in the aquarium at night to see them scurrying on their urgent errands. So any food that gets into the rocks is food for them.

I have never had any nitrate or phosphate reading. If they are there, they are undetectable on my test kits. The zero phosphate is probably down to the fact that I have always had an anti-phosphate filter running, with properly timed media changes. When the aquarium commenced bio-filtration was by canister filters, and of course the nitrogen cycle stops after the creation of nitrate with canisters. This is why I used a homemade anti-nitrate filter in the beginning. Maybe routine seawater changing helped plus the fact the fish load as now was low. The inert porous rock I used to build the reef is now live, and so any nitrate should be controlled naturally. The anti-nitrate filter was turned off over two years ago and a nitrate reading has never appeared.