Going with the Flow: Keeping Hillstream Loaches
Mike Hellweg
Aquarium hobbyists are always on the lookout for something new and different. We tend to seek out cute or unusual behaviors, old favorites, oddballs, bright colors, and interesting patterns. Any number of different characteristics can go into what makes a “must have” fish for a particular fishkeeper.
The group of fishes known as the hillstream loaches boasts a combination of several of these characteristics, and they can provide something of interest for most hobbyists. This has turned out to be the case most especially for the ever-growing group of planted tank aficionados among us.
Loaches have been incredibly popular in the hobby for decades. In the early to mid-1990s, a few very different loaches started showing up on import lists from Southeast Asia and in the mom-and-pop shops. They were assigned common names based on a combination of where they came from and their resemblance to the popular catfish we know as plecos: Borneo pleco, Vietnamese pleco, Taiwan pleco, etc.
You get the idea. But not only were they not plecos, they weren’t even catfish.
Some Natural History
Hillstream loaches are more closely related to the loaches, but they are actually in their own separate family, Gastromyzontidae. Currently, there are nearly 150 species and 18 genera in the family, but more are being described all the time, and it seems we have only scratched the surface. About a dozen of these fishes are found fairly regularly in the hobby, and many are being bred with some regularity.In the wild, hillstream loaches are found in cooler, flowing streams from China throughout Southeast Asia. Some are even found in rocky streams on the islands of Borneo and Taiwan, with likely many more yet to be discovered.
Regarding hillstream loach diet, the majority of the known species feed on the layer of algae and bacteria on the rocks of their home streams, which we hobbyists call aufwuchs. Some may tend toward consuming more meat in the form of benthic invertebrates, while others tend more toward a vegetarian diet of algae, but in general they are omnivores.
Early on, hobbyists discovered that these fish seemed to do much better in older, more established tanks. When put into a clean new setup, they often failed to flourish. This fits in with their being aufwuchs-eaters, since older tanks would have a much more extensive and healthier layer of biofilm.
Hillstream loaches also seemed to prefer being kept in groups. Single fish typically languish and die within a few months. Among groups, while there was considerable scrapping and jockeying for favorite positions in the tank, especially in or near the flow of the filter, little harm is done and the groups usually do well.
One unique problem that those of us with waterfall-type hang-on filters came across was that our entire group of fish could disappear for a few days, only to turn up in the filter when we broke it down to clean. It was quite a surprise to me, back then, to first discover that they liked to climb.
I soon learned that they would even clamber up the sides of a bucket during acclimation. So, from that point on, I used a small plastic tank with a mess lid inside the bucket when drip-acclimating them. I’ve never kept them in an open-topped rimless tank, but I suspect that they would eventually climb out of one of those.
Another thing we early adopters figured out: If you keep a group of them, all purchased at the same time as the same species, in an older tank with the larger, old-school “pea” gravel, fry will sometimes turn up with no other work on your part.
Feeding & Grazing
Along with their grazing every surface in the tank, they also enjoy sinking tablets and pellet-type foods, gel foods, and various frozen foods, and they will even consume live worms. If you have active-feeding tankmates for hillstream loaches swimming in the upper water levels, make extra effort to get some food to the bottom for the loaches. Pro tip: a piece of PVC pipe can be inserted into the water column, and some pellets can be poured to the bottom for the loaches, without the upper-level fish being any the wiser.
In their early days as aquarium fishes, the thinking was that, since they were hillstream dwellers, they would prefer faster-flowing water, but we now know that strong filtration is unnecessary. As long as the water is clean, low in dissolved organics, and well oxygenated, these fish will do just fine with slower flow.
My preferred method is using a sponge filter, specifically a Mattenfilter, and it seems to be ideal for hillstream loach care. By design, once established, these surface-rich filters are covered with the aufwuchs and microscopic food perfect for any hillstream loach’s diet.
Tank Setup
These fish do prefer cooler water, so heaters are not necessary. Room-temperature water is fine, and the daily and seasonal fluctuations in aquarium temperatures seem to be to their liking. Cooler water also holds more oxygen than warmer water, so keeping them cooler takes care of two needs at once.
Over much of the area where they are found, the water has a pH below 7.0 and is softer, but in captivity they’re not so demanding. I’ve known hobbyists with hard, alkaline water who have successfully kept and bred several species, as well as others who have more neutral, softer water and have likewise had success. Concentrate more on large, regular water changes and keeping the water “clean” than on trying to hit a specific water parameter.
Unlike many of their nocturnal loach cousins, hillstream loaches are diurnal and love bright light. They will spend the entire day out and exploring their tank. They even seem to be aware of their keeper and what is going on outside the aquarium, as evidenced by how they get used to their feeding schedule and watch for the rain of delectables at dinnertime.
A perfect tank for them is long and low, as hillstream loaches are bottom-oriented and spend their time exploring every surface. In a long, shallow setup it is easy to create a directional flow with a Mattenfilter covering one end with the outflow pointing to the opposite end.
For substrate, I like a sand bottom with a pile of pea gravel topped with small cobbles piled along the base of the Mattenfilter, as well as several larger cobbles or rounded stones piled around the tank that mimic a rocky stream bottom.
The pile of pea gravel and larger stones provides a place for the eggs and young fish to find refuge among the crevices, as well as food while they grow. Piling it up at the base of the Mattenfilter allows the return flow to pull the eggs, the fry, and their food to the same place right at the base of the filter’s surface, which is covered with microscopic food.
These fish don’t need plants, but they certainly seem to enjoy exploring the leaf surfaces for food all day long. Larger-leaved plants like Anubias, Cryptocoryne, Java fern, and even swords and Aponogeton are particular favorites, but the ever-growing number of aquascaping fans have found that they’re just as happy in any type of densely planted tank.
They make good community tank residents. Rainbowfish, danios, tetras, minnows, barbs, and similar active but peaceful schooling fish make perfect hillstream loach tankmates. Livebearers, on the other hand, will compete with the hillstream loaches for aufwuchs, so it’s best to leave them out.
Reproduction
Sexually mature male hillstream loaches have a larger head and usually a more colorful dorsal fin. Some males have seasonal bumps that show up on the front ray of their pectoral fin, and they often skirmish with other males.
While “fights” are common and often followed by mad dashes around the tank, no harm is done to the opponent. It’s likely that this behavior gets the hormones flowing, sort of like the more familiar rutting observed in deer, and it might even be necessary for some species before spawning.
The males also display for females, doing a sort of dance in front of them and showing off their dorsal fin. Sexually mature females usually have smaller heads and a thicker bodies behind their dorsal fins.
Provided there are males and females in the group, housed in a tank set up as described above, and no potential fry predators, a group of a half-dozen or more happy adult hillstream loaches will do what comes naturally and spawn.
Many of the species I’ve bred so far fall into one of two categories: egg scatterers and cave spawners. Spawning is rarely witnessed, and the first sign of a spawn will usually not be evident until you see baby fish scouring the rocks.
Breeding Egg Scatterers
I have not witnessed the spawning of the egg scatterers, though it is reported that a male and female swim up into the water column and perform a kind of twisting dance that mixes eggs and milt as they are released. The eggs then flow with the current to the bottom and get lost in the crevices of the gravel.
The fry hatch in a couple of days, and they spend their first week or two grazing in the gravel for microscopic life of all kinds. As they grow larger, around a half-inch long, they begin to spend more and more time grazing on surfaces out in the open. The adults tend not to be interested in either the eggs or the fry, and in a good-sized tank without egg or fry predators, you can wind up with several hundred hillstream loaches over time.
You certainly don’t need to be an expert breeder to get these fish to reproduce prolifically. I have had a couple of customers contact me over the years who wanted me to come collect their multitude of “plecos,” only to arrive and find out that the fish were actually hillstream loaches. I once pulled more than 200 small Sewellia lineolata from a customer’s planted tank!
Once the cave is acceptable to the female, she will enter about halfway, roll over, and lay a clutch of eggs on the roof of the cave. The male will then move in and fertilize the eggs. After that he usually moves out, either filling in the cave or covering the eggs with sand.
A few hobbyists have reported that their males have actually sat in the cave and guarded the eggs, but I have not witnessed it myself. Either way, after hatching, the fry move into the substrate for a week or so, feeding on the microscopic life found within until they make an appearance among the adults in the tank.
Unique, Interesting, and Easy to Keep
If you’re looking for something a bit unusual, definitely unique, sometimes a bit colorful, yet easy to care for and active out in the open in your tank, don’t hesitate to try keeping a group of hillstream loaches. And, as always, don’t forget to spend time just sitting and watching your fish. After all, isn’t that why we all got into this wonderful hobby in the first place?
