Federation of British Aquatic Societies

My real passion in tropical fish is Corydoras but, like most fishkeepers, I can't resist the odd 'non-Cory' so consequently my tanks now hold many types of Characin, Dwarf Cichlids, a few Discus and Otocinclus.

The Otocinclus were obtained from three separate sources – two shops and an Auction – the idea being that they might keep one of my stock tanks free from algae. I soon learned that you would have to fill the tank to regulate the algae growth, as my nine fish seemed to graze all day with no effect at all!

After a major reshuffle in my fish room, a suitable breeding tank became available for the Otocinclus so they were caught up and transferred to the breeding tank, set up using an air-driven foam filter with several pieces of Java fern on bogwood, and a thin layer of play pit sand.
Water conditions were 25^oC, slightly acidic and soft – my usual starting point for South American species.

Food at this time was TabiMin, frozen Bloodworm and Mysis Shrimp (the Bloodworm and Mysis were both grated whilst still frozen).

It soon became apparent that not all the fish were the same type, a size and markings difference led me to believe that I had two types of Otos, so out with the books to identify them.

At this point, a major problem cropped up: firstly, there does not seem to be much information about Otos and, secondly, as they started to come into condition their colour and markings changed significantly, making it even more difficult to find them in my books or on the Internet.

But, after much searching, I believe I have O.vittatus and possibly O.vestitus (maybe!).

During the search I had hoped to discover more about the natural environment for these fish, water conditions, food etc., but my water conditions were close anyway, so that left food; my book said they eat 'aufwuchs' but I don't think my shop stocks 'aufwuchs' – and I'm not sure I dare ask them!

The Otos were split into species groups and housed in two tanks with exactly the same conditions. I now started to try lots of different foods as well as the food already mentioned; I tried newly-hatched brine Shrimp, Microworms, Grindalworms and chopped Whiteworms and very fine high-protein fry food which the fish would harvest from the plant leaves as they searched for algae,
all of which were readily eaten.

I also tried cucumber, lettuce and potato but the Otos ignored them preferring to eat algae. It should also be remembered that heavy feeding can quickly pollute the water so I started changing 10% of the water every day and 50% once a week.

After a couple of weeks of this regime, my Otos had undergone a complete change. The females showed full abdomens and the males competed to be next to them, pushing each other out of the way to be near the largest female.

I did not witness a spawning, but it became obvious when it was about to happen as the males would chase all around the tank to be the one to fertilise the eggs, which were always placed on plant leaves and usually out of sight, unlike Corydoras I never found an egg on the sides of the tank.

After a few days, young fry could be seen all over the tank, on the glass, on the plants and on the sand base. They were very small and I was concerned as to what they would eat, but it became clear they were grazing on the bio-film that occurs naturally in an established tank (bio-film probably consists of algae, bacteria and micro-organisms, the nearest I could get to 'aufwuchs'). The fry grew at a good rate and were soon eating the same food as the adults.

Every few weeks a new hatch would appear and it soon became obvious that I would have to stop the adults spawning or run out of room, so I moved the adults back into the stock tank to allow the youngsters room to grow, and grow they did, within a few months I had two very full tanks of young Otos to find homes for.

Eventually, all were sold at auctions and I hope they gave their new keepers as much enjoyment as they did me.