Matt Clarke answers some common questions on the mochokid catfish genus Synodontis.
What are Synodontis?
Synodontis is a genus of upside-down catfishes. They are members of the African catfish family Mochokidae which contains about 150 different species in 10 genera.
The genus Synodontis is by far the largest and most well known in the family, and dozens of species are available in the hobby, ranging in size from just a few cm to well over 30cm/12".
Why do they swim upside-down?
The true Upside-down catfish, Synodontis nigriventris, is adapted for feeding from the surface on insects and other items that fall into the water.
If you look closely at this species, you'll notice that it's cunningly disguised to be less visible to aerial predators, like birds, and to fish swimming below it.
Most fish have a cryptic colour pattern called countershading and their backs are darker than their bellies, making them more difficult for predators to see. But because Synodontis swim the wrong way up, they use reverse-countershading so that their bellies are darker than their backs.
Do all Synodontis swim the wrong way up?
Some swim upside-down more than others (some hardly ever do it), and many babies don't start swimming upside-down until they are two or three months old.
What sort of set-up do I need?
It depends on the size of the fish and whether it's a softwater species or one of the East African Lake fishes. Most are crepuscular (most active at dawn and dusk) so provide plenty of daytime shelter. The West African ones do well in a tank containing lots of bogwood, while the East African ones do best in a much rockier set-up. A sandy substrate is a good idea for keeping their sensitive barbels in good condition.
Can I keep them with other fishes?
Synodontis generally mix well with other fishes and are easy to keep. Larger ones could eat very small fishes, and they are often quite territorial towards other catfishes, especially other synos.
If you are keeping several Synodontis in the same tank, ensure that you provide plenty of hiding places and have a spacious aquarium.
Which ones are best for smaller aquaria?
Some mochokids are ideal for smaller tanks, even as small as 45cm/18" or so. The true Upside-down catfish, S. nigriventris, grows to about 6cm/2" on average and can be kept in a small group in a smallish or medium-sized tank.
Payne's catfish, Mochokiella paynei, is very pretty and worth looking for. This fish only reaches about 7cm/3" at most and likes neutral or slightly acidic water. It is peaceful and has spawned in aquaria on occasions. Some tiny ones, such as Microsynodontis, do turn up from time to time.
Are they easy to get hold of?
Most of the common species, including S. nigriventris, S. decorus, S. eupterus and S. multipunctatus are available throughout the year as many are produced on fish farms around the world.
Summer and autumn are generally the best times to get hold of the rarer species, as imports from Nigeria and Cameroon seem more regular at this time of the year.
My Upside-down catfish is growing much larger than it should. Have I been sold the wrong species?
Yes. The real Upside-down catfish, S. nigriventris, is imported in large quantities and lives in big shoals. You'll often get other species mixed up in the same import, so you can often mistakenly buy the wrong fish - S. nigrita and S. robbianus are quite commonly mis-sold as nigriventris, but you may also come across other species too.
I think I may be experiencing auditory hallucinations. I am convinced I have heard my Synodontis squeaking at me.
Don't worry. Synodontis do sometimes make noises that are audible outside the aquarium. This has earned them the name 'squeakers' in parts of Africa.
They make croaking noises at each other using their swimbladders as a warning to other fishes encroaching on their territory.
Are there any unusual ones around at the moment?
Yes. A few unusual ones have surfaced in British shops in the past year or so. Some of the most interesting are those from Lake Tanganyika. Many of these look like existing species, including S. multipunctatus, S. polli and S. petricola but have some subtle differences in morphology and colouration.
There are also a couple of fish appearing in the shops that some retailers believe may be of hybrid origin. And there are rumours circulating that the fish have been produced by breeders in the Czech Republic using hormone injections to trigger reproduction.
Also look out for Synodontis sp. 'Golden Eye', which is a bit like Synodontis multipunctatus. It's being bred in the UK and some specialist stores are stocking the very attractive juveniles. Look out in this mag next month for more details.
This article was first published in the September 2003 issue of Practical Fishkeeping magazine.