Rainbow Fishes

By Joan Davidson 1989

Photo By: Matthius Lettington

Easy or not so easy?

Up until about five years ago the only Rainbow fishes for sale in this country on a regular basis were, the Madagascar rainbow Bedotia Geayi and the Celebes Rainbow, with the occasional import of the two Australian Rainbows, Melanotaenia nigrans and maccullochi. Then suddenly five years ago we were flooded with fishes from Australia and Papua New Guinea. As usual northern fishkeepers were not initially aware of this sudden upsurgeof fish on the market. However shops in London and the Southern Counties had sometimes as many as 20 different types in their shop at one time.

Articles in the fish press in this country were as usual non existtant although T.F.H in their monthly magazine, did several articles on the collecting and keeping of these fishes. All the articles seemed to lead us to believe that the keeping and breeding of these fishes is comparatively easy, but after several years keeping and breeding them I and several friends are not so sure. So I put down some of the pros and cons and I shall let you make up your own minds.

The Pros 

Firstly there is something for everyone in the Rainbow family, if you want small and peaceful with delicate colours and fabulous fins there's Iratherina werneri. If small and brilliantly coloured take your fancy there is the Pseudomogills. In the larger fishesof the Melamotaeia, Chilatherina and Glossolepis families the colours are striking.

Secondly these fishes in most cases are tolerant of a wide range of water conditions, hard or soft, acid or alkaline, they dont seem to mind. As far as food goes their appitites are never satisfied, in some cases jumping out of the water in their greed and stunning themselves on the cover glasses. The only thing I find non of the Raibows are keen on is tubifex, in some cases they will not eat it whether live or frozen.

Thirdly the Rainbows are easy to sex, and in most cases easy to spawn. In the smaller species the colours and fins tell all. In the Melanotaenia, Chilatherina and Glossolepis the mature fish are easy to tell by their colour, However the fish are quite easy to sex by the following method when young and showing no obvious colour and shape differences. Look at the fish from the side when the two dorsals are laid flat along its back, if the first dorsal touches or overlaps the second dorsal, the fish will almost certainly be male, the females first dorsal will not touch the second dorsal. Once you have looked at a few you will see how easy it is to tell. Just occasionally you will get a late developing male, but on the whole this method is very relilable.

As far as breeding goes once they start spawning they never seem to stop. The simplest method I have found is to use nylon mops as used in killi fish spawning. If a large spawning is required place a few pairs in a largish tank, feed well and the fish will lay a number of eggs every day on the mops. I have not found that Rainbows eat their eggs, so I tend to leave the fish with the mops for 8 days when the eggs should be about to hatch. It is then up to you whether you remove the fish or the eggs. In the case of the smaller Rainbows I would remove the fish, as the eggs aren't as robust as the larger Rainbowfish.

When the fry first hatch, they swim jerkily around the tank, when they swim correctly and can sit in the water without sinking they are ready for food, this is only a few hours after birth. The fry of the larger Rainbows will eat brine shrimp straight away, but the smaller ones need infusoria. The larger Rainbows will cross breed quite happily, this of coarse should not be allowed to happen. Make sure when buying Rainbows that you are given their correct Latin name and if possible their location as fish from different lakes and rivers should be kept seperate if possible. Well you're probably thinking it all seems pretty straight foward what's the problem.

The Cons

The Melanotaenia boesmani I saw were about 7 inches long, these were newly imported fish the intense colour of the blue at the back and the dramatic yellow at the front I have never seen since. Why we haven't seen any is a good question. The fish available seem to be small, poorly coloured individuals and not very robust. In the last three years I have not seen a boesmani over three inches including in my own tanks, obviously something either in our water quality or our feeding is not right.

I found the boesmani to like clean old water and be very susceptable to sudden changes of water quality. A change of 6 Gal in a 40 gal tank could upset them for days. They would go off their food and in certain cases close their fins and 'shimmy' like Mollies.

In bad water they develop fungal growths around their pectorsal fins. In some of the other speciesof Melaotaenia, Chilatherina and certainly in Glossolepis incisus we are losing size. We are also losing colour not only in the body and fins but band of colour from the nose to the dorsal fin which the males flash like a light seems to be fading and in some types disapearing all together.

Another anomily of these fish is that you can have a tank of mixed community fish which includes Rainbows when, for no apparent reason the rainbows will start dying. The fish can be in full breeding colour, but a couple of hours later they will be dead, still in colour and with no marks on them. All the other fish will be showing no signs of distress, and other than an increase in respiration if watched the Rainbows show no signs of distress either. Water quality is of course the first thing that comes to mind but, even large water changes with clean well matured water has no effect. All medication seems ineffective, but if you catch all the fish and tranfer them to another tank, the fish stop dying.

If anyone can throw any light on this I will be more than pleased to hear from them. The Pseudomugils are also not also not easy to keep you always seem to end up with one sex or other, don't ask me why. The Iriatherina werneri are not too hard to keep, liking old water with not a lot of movement, however their fry are very difficult to raise, they are very tiny and very idle not going looking for food. The only person who I know who does it with good success does it on all dry food after the infusoria stage, and keeps them in small bare tanks, he only does very small water changes.

So there are some of the pros and cons of keeping the Rainbow fishes, I hope I haven't put you off, maybe it will be easy for you if not they're well worth the challenge.

Back To Species Selection