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Breeding Sewellia

by Martin Thoene last modified Feb 09, 2008 11:24 AM

Credit: Emma Turner


  It is easy to see why the Reticulated Hillstream Loach, Sewellia lineolata, caused such a stir when pictures first circulated on the internet, before exports from its native Vietnam began. Not only did this extraordinary fish instantly appeal to the ‘hardcore hillstream loach enthusiasts’, but to the fishkeeping world in general. Their outstanding dark markings on a bright yellow background colour are enough to rival any South American L-number pleco!

Maidenhead Aquatics - Sewellia lineolata In August 2005, Maidenhead Aquatics @ Peterborough were the first store in the UK to import this species.

  The shipment arrived on the whole, in very good order, and several weeks later, all still being well, I purchased 8 specimens for my River Tank. This aquarium was set up some months previously based upon Martin Thoene’s excellent uni-directional flow design, as featured here: Hillstream Loaches - The Specialists at Life In The Fast Lane. The River Tank principle not only encompasses this very natural one way flow as found in most large river systems, but also creates a very high level of oxygenation due to the amount of water movement involved – absolutely essential for keeping any type of hillstream loaches successfully. Other occupants of my River Tank at the time were two large adult Schistura balteata, Amano plant shrimps (Caridina multidentata), Eight Banded False Barbs (Eirmotus octozona), Danio sp. ‘Hikari’, and a couple of unidentified hillstream loach species, also from Vietnam (possibly one Annamia and one Homaloptera species).

Maidenhead Aquatics - Emma & Steve's River-Tank    The aquarium itself has a fine black sand substrate and many bogwood pieces, with smooth Scottish cobbles placed on the sand around the bases of the pieces of bogwood. Hillstream loaches have evolved to ‘hang on’ in fast flowing currents and graze on the algae that forms on rounded or smooth flat stones. As S. lineolata originate from boulder-strewn streams, I considered these smooth stones an absolute must for their wellbeing. I have several plant species that do surprisingly well under the extreme conditions in this river-style set up. Plants are not essential, as they are not found in abundance in the areas S. lineolata inhabit in the wild, but they can help with water quality and do look aesthetically pleasing. Anubias barteri, whilst slow-growing, always fares very well in most River Tanks, my plants being trained to grow on the bogwood along with Java moss, which always requires regular pruning. Cryptocoryne balansae and C. wendtii ‘green’ are planted in the gaps between the cobbles and have been growing remarkably well for some years now. As mentioned in the previous article, bright lighting is essential for all river tanks as it promotes decent algal growth over the cobbles and other décor. Hillstream loaches enjoy grazing this for the small micro-organisms it contains. The other crucial factor in the maintenance of this species is its preference for almost sub-tropical temperatures, to mimic the cooler hillstreams in which it naturally occurs.


The Flutter of Tiny Fins


During the football World Cup of May/June 2006, I was carrying out some routine maintenance on the tank. Don’t get me wrong, I love football (I’m a loyal Norwich City fan!), but with the multitude of matches that were on in the early stages of the tournament, I kind of had ‘football overload’ and so left my other half watching the match whilst I attended to the external filter. The filter I use on this 180 litre tank is an Eheim Pro II 2028, which houses three media trays. With my attention wandering between filter maintenance and the match, I absentmindedly removed the top tray which held the phosphate-remover, Indian almond leaves, and fine filter wool. I then started to lift out the second tray, but stopped mid-way through to glance over at the TV. When I looked back down, I saw something tiny dart about between the ceramic media! I mentioned this to the football-engrossed other-half and just met with an, “Mmmm” type of ‘non-interested, eyes-fixed-on-telly reply’, like it was my wild imagination playing up again. I stared back down at the tray, still submerged in the filter, and saw not one, but several small fish darting about. After a bit more persuasion, I prized Steve away from the television in a fit of mad excited-ness! These fish could be loaches!
    We hurriedly retrieved a small 12” x 8” tank that I normally use for photographing fish at Steve’s shop ( and set it up using water from the main aquarium and an Interpet air-driven sponge filter. I actually use four replacement Interpet sponges on the intake end of my River-Tank manifold, so swapping one of the old ones for a new one, I quickly (and very conveniently) had an established sponge to run on the little filter in the baby tank.
    The fry were tiny, 6mm TL maximum, and very difficult to catch. They would keep darting down between various ceramic tubes and balls in the bottom two trays, and so we literally had to remove the media piece by piece to minimize the risk of them becoming hurt when trying to net them out for transfer to the small tank.

The following four photographs were taken on
 16th June 2006
 Sewellia fry21  Sewellia fry22
Sewellia fry19 Sewellia fry20

There turned out to be nine fry in total, and as they had began their lives in the darkness amongst the filter media, I decided to leave various bits and pieces of ceramic media in the baby tank as a temporary substrate for them to browse on and hide amongst. I did not add any lighting to this tank either.
    At this point, I didn’t know for sure which species had bred, as the tiny fry bore no resemblance to any of the adult fish. As regular Loaches Online members will remember, I posted some photographs on the website : Here

(Some images may no longer be shown in-thread, but are in this article)

A really exciting guessing game began! The only recent addition to the tank had been a few female S. lineolata, as most of my original group had turned out to be males.

Sewellia fry3 Because of the relatively slender appearance and the presence of obvious barbels, many people were swift to assume they were likely to be Schistura balteata fry.
(24th June 2006)

 However, as my series of developmental photographs show, the fry changed dramatically over a short period of time and it became apparent that these were actually a sucker-belly type hillstream loach, not only from the markings and ‘shrinking’ of barbels, but by their sudden ability to ‘cling’ to the glass and décor using their modified pectoral and ventral fins. Photograph opportunities were not always easy, due to the secretive nature of the fry.

    To sidetrack slightly, shortly after this event, I managed to acquire a new and currently undescribed species of Sewellia, which we have been referring to as Sewellia

sp. ‘spotted’ due to the fact that these fish are of a dark base colour with a splattering of fine yellow dotted markings all over.

Sewellia sp. "Spotted"

Sewellia sp. "spotted"

These were said to occur in a location that overlaps that of S. lineolata, but we do not have any real proof that this is the case. All we know for sure is that they are Vietnamese and are wider and more heavily-bodied than S. lineolata. Unlike S. lineolata these fish are quite a cryptic species that remain hidden for most of the day, and only really venture out in the open with confidence when under blue moon lights or an absence of lighting altogether. S. lineolata adults are the opposite, and are always present, even under the brightest of lighting.

Sewellia fry4 29th June 2006
Sewellia fry5 29th June 2006
Sewellia fry6 10th July 2006
Sewellia fry7 7th August 2006
Sewellia fry9 25th August 2006
Sewellia fry10 25th August 2006

Dark coloured after just moving from dark substrate.
Sewellia fry12 28th August 2006

New fry in main tank.
  Several months on, and at a TL of 20mm, I decided to prepare the S. lineolata fry for transferral to the aquarium in which they had originally been conceived. I added a small Maxijet powerhead (complete with impeller protection cage) to the fry aquarium to give an increased flow rate. Sewellia fry8

After a short period of adaptation, the young were obviously enjoying this new found current and were able to move about fantastically well.


  I decided to give away three of these fry to loach-keeping friend Graeme Robson before moving the remainder across, and the evening before he drove down to pick them up, I spotted a new single little fry in a large Anubias plant in the main tank itself!
(8th December 2006)
Sewellia fry13

 This fry was much smaller and clearly from another spawning, which once again I had failed to witness. I was amazed at how it must have managed to survive in there, running the ‘Schistura gauntlet’.

Sewellia fry14 The six remaining fry in the baby tank were acclimatised across and the small tank dismantled. The River Tank became a hive of activity with the little ones checking out their larger counterparts. I admit to being quite concerned about moving them across after nurturing them for some months, but I needn’t have worried!
(8th December 2006)

   The next evening, I was relaxing in front of the River Tank, observing the newly-transferred fry. Suddenly something caught my eye on the sand behind a hunk of bogwood. At no more than 5mm TL, this young fish had a bright yellow base colour with several jet black bars – completely different to the S. lineolata fry! Although concerned for its safety (it could easily have fitted in the mouths of those Schistura!) I tried to console myself with the fact that if it had survived to that stage, it should have a good idea by now of how to remain safe.

    Thinking that it might be prudent to check the filter once more, I opened it up to find another thirteen S. lineolata fry in the bottom, this time under the media trays. No sign of any more of these stripy fellows though. So less than 24 hours after dismantling the fry tank, I found myself setting it back up again for these youngsters. There were two different sizes in this collection, evidence of more than one spawning.

    Those thirteen S. lineolata grew well on a diet of Interpet Liquifry No. 3 finely powdered fry food, crushed JMC catfish pellets, Tetra Prima Mini Granules, frozen cyclops and baby brineshrimp. Exactly like the previous batch, these fry began clinging to surfaces at an early stage in their development and are fairly reclusive (much unlike the adults of the species).

10th December 2006
Sewellia fry15
12th December 2006
Sewellia fry16
16th December 2006

Two youngsters fighting with one another.
Sewellia fry16a
5th January 2007

Size comparison with adult female.
Sewellia fry17
11th January 2007

Adult female with baby.
Sewellia fry18
11th January 2007
Sewellia fry18a

    Conversely, the mystery stripy fry had not been attempting to cling very much, instead spending much of its time out in the open, foraging about on the sand. Its markings changed dramatically, and it would be several weeks before it began to cling. At that point I was confident that I had also managed to spawn the Sewellia sp. ‘spotted’ and have even found a second stripy fry (smaller) from another spawning! Must have been all those hormones floating about in the water!


    Water parameters in the River Tank at the time of the first spawning were as follows: pH=6.6, dH=5 degrees, Nitrates=5-10ppm, Temperature=25 deg C.

    It had been assumed that S. lineolata, being a member of the Balitoridae family, might spawn in a similar way to that of its Chinese cousins, the Pseudogastromyzon species. P. cheni has been bred successfully in captivity by several accomplished aquarists, and observations of the actual spawning process have been made on a number of occasions. Pseudogastromyzon are known as ‘pit diggers’. During courtship, the male dances around the female, and when accepted by her, he digs a pit in the substrate by sliding backwards off of a cobble and swishing his tail to dig a hole. The female lays her eggs in this hole, which the male then fertilizes, and after spawning has ceased, he covers the eggs up with the substrate. Approximately two weeks later, the fry emerge. Despite many hours spent glued to the antics inside my River Tank, I saw no evidence of such behaviour in my Sewellia lineolata.
Five months after I spawned my loaches, a German aquarist claimed to have bred S. lineolata in his tank. He said that he witnessed a male and female rising up to the water’s surface, entwining their bodies around each other and releasing a fine spray of eggs/milt into the aquarium. This was, at first, met with a little skepticism, as many people were still of the impression that S. lineolata were most likely to be pit diggers. However, the designer of the River Tank aquarium himself, Mr Martin Thoene, since observed his S. lineolata spawning in the same manner as the German aquarist. Sadly though, to date no fry have survived his initial observed spawning, although I’m sure it won’t be long until this happens. Since compiling this article, I too, have been privileged to witness a spawn (almost a year after finding my first fry) and concur with these reports. My observations followed a small partial water change, with the courtship behaviour starting a few hours later under blue moon lighting conditions. The male spent a long time trying to entice females into a small defended territory, and if she decided to stay, he would circle her again and again until she either swam away or accepted him. When a female did eventually accept him, and after 20 minutes or so of circle dancing and tender nibbling of the dorsal surface, they rose high up into the water column together, bodies absolutely rigid as they did so. They even appeared to be interlocked by one set of opposing pectoral fins (i.e. the females’ left pectoral and the males’ right pectoral). My River Tank is taller than may be conventional for these type of set ups and the fish were almost at the water’s surface when the eggs/milt were simultaneously released.
Looking back, this method of spawning does make great sense, as S. lineolata inhabit boulder-strewn waters where there is little or no substrate to dig into.

Sewellia lineolata, groups in natural stream. Sewellia lineolata in natural stream. Note hard rock base with no substrate.

It would follow, then, that the fish do rise up in the water column in their embrace, releasing the eggs/milt into the water to hopefully flow downstream to a place of safety where they can develop on to adulthood. It also explains why my external filter ends up drawing some of the fertilized eggs in, where most of the fry have begun their lives!

Sewellia lineolata - two males fighting Sewellia sp. "spotted"
Sewellia lineolata
Sewellia sp. "Spotted"

To all Sewellia keepers out there: When carrying out aquarium maintenance, never throw away the water inside your external filter without examining the contents first!


Emma Turner

Sewellia fry composite

Images: First photograph: Martin Thoene (taken @ Maidenhead Aquatics)

             River-Tank photo: Martin Thoene

             Natural stream photo: Miroslav Farkak, of Saigon Aquarium Corp

             All other photos : Emma Turner

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