Would you fork out good money on what some say looks like a moody worm? Many loach keepers would. Here's our guide to maassi loach and how best to care for them, including the recommended tank set up, some helpful tips on feeding and whether they play well with other fish...
The Maassi Loach (Vaillantella maassi) is something of a grail species for the loach hobbyist. At first glance, and to the inexpert eye, it probably looks like some Pangio castaway, minus the attractive orange embellishments. Get closer and you’ll see plenty of anomalies on a distinctly unique fish. There’s the vast dorsal fin running down the back like some inverted knifefish. There’s the long and deeply forked caudal fin, something you’d expect to see more on high-speed pelagic species rather than a bottom dweller. And if you get really close, you might note the absence of the mobile ‘eye spine’ that’s the bane of many a loach catcher. The genus this loach belongs to—Vaillantella—even has its own family, the Vaillantellidae, given that the fish just doesn’t taxonomically fit anywhere else.
Maassi Loach Fact File
Scientific name: Vaillantella maassi
Pronunciation: Vay-lan-tell-ah mah-see
Size: To 12.5cm
Origin: Borneo, Peninsular Malaysia, Thailand, and Sumatra
Habitat: Blackwater, flowing rivers of silt or peat, sand and tree roots
Tank size: 80x30x30cm (for an individual)
Water requirements: Soft and acidic to neutral water; 3.0-7.2pH, 0-12°H
Temperature: 24-28°C
Temperament: Territorial, bordering on aggressive with random tankmates
Feeding: Small meaty foods like Daphnia, bloodworm and tubifex, as well as colour enhancing pellets
Availability and cost: A real rarity, expect to pay somewhere around £40 per fish if you can find them
Maassi Loach Diet and feeding
The diet for maassi loach should be richly meaty, and with emphasis on including come colour enhancers where you can. Part of the maassi loach’s appeal is the bright dorsal line that can vary its intensity based on what the fish is fed. Pale, washed out yellow lines are obvious in fish with insipid diets, while fiery oranges bordering on red are found in those offered a carotenoid-heavy menu. Colour enhancing sinking pellets (you’re looking for beta carotene the ingredients) will be taken and will keep things looking vibrant. For the mainstay of mealtime, you want to introduce as many live and frozen treats as you can, however. Bloodworm is readily taken, as is tubifex (although the UK is experiencing something of a tubifex drought in 2023, due to supply problems at source). There’s a hint of oophagy going on too, so don’t be surprised if any breeding fish in your tank have their eggs snapped up in the night.
The night is when everything happens. Although food will tempt them out during daylight, night is when the fish become more active. LED lights with a red or blue setting will be valuable if you wish to see your maassi roaming after dark.
Top feeding tip for maassi loach - Adult maassi loach are capable of eating small fish and fry, and will do so if given the chance. Monitor your livestock as they grow and adjust accordingly.
Related article: A quick guide to loaches
Tank set up and habitat for maassi loaches
What does a tank for these fish look like? Set up as a biotope, it would be large (in the region of 100cm or more) with a sand substrate, lots of plants, lots of leaf litter, dim or subdued lighting, and stocked with a few maassi loaches alongside other loaches (especially Pangio) as well as fishes that live higher in the water column—gouramis, barbs, rasboras and danios would be reasonably biotope correct. With Vaillantellia hailing from Borneo, Peninsular Malaysia, Thailand, and Sumatra, you have a good selection of biotope-correct fish you could use. As a point of interest, strong flows should be avoided. While the maassi loach originate from high-speed habitats, they don’t attack the water head on. Rather, they find quieter recesses, and that’s what you’re aiming to recreate.
Top tank tip for maassi loach - Always keep a Vaillantella tank permanently covered. Night time escapes by jumping will soon occur in an open-topped aquarium.
More pragmatically, they tend to do fine in community tanks that provide plenty of cover and have a pH on the acidic side of neutral. Housed away from fish that might nip them (that long, forked tail is tempting to many) and with a small plot to call their own, they’ll settle in and only show their heads at feeding time. You’ll do well to avoid slow-learning fish (like Corydoras) that fail to understand territorial boundaries, as they’ll keep stumbling into the firing line, to the annoyance of all parties. Given the prohibitive price, these ‘community maassi’ tend to be kept individually, and as such smaller tanks of 80cm fit the bill.
Some tough plants with a root structure that runs above the substrate (think the classics of Anubias and Java fern) will give them something to rummage through, while some scattered leaves will increase the chances of them moving about in the daytime. Floating plants aren’t found in the streams they inhabit, and so are somewhat alien in the home setting, but the strategic positioning of dense plants higher up in the tank will help to create shadowy areas.
And there we have the fish that drives loach fanatics wild. They’re scarce because they either comes in as by-catch, or deliberate efforts to hunt it involve placing nets downstream and stomping the fish out of the undergrowth. But if you can find one, you’ll be the envy of the (loach) town.
Do maassi loach make good tank mates?
Whether they belligerently defend it or not, they do like to stake a claim to a territory, and once they’ve found a spot they like, maassi loach rarely stray from it until the lights go out. A cluster of rounded rocks will become a home, although leaf litter—especially a deep bed of various decaying leaves—will really excite them.
Wild fish are found in a range of conditions. Collector reports typically mention fast and flowing water (which makes sense given the fish’s powerful tail), although slow and even stagnant water catches aren’t unknown. What seems relatively constant is that the water they inhabit is clear (i.e. without floating particles), acidic and stained. Many of their native rivers have their origins in peaty substrates, causing the water to become saturated with tannins. While natural conditions can see the pH of their water fall as low as 3.5, in aquaria they can sit somewhere closer to neutral (upper limits seem to be 7.2pH). For the sake of biological filtration (which can struggle to function as the pH plunges) and ease of care, a tank set to 6.5pH would be a sensible goal.
Substrate is important with any bottom dweller, and while maassi loaches don’t bury themselves as often as some other loaches, a soft substrate of fine sand will drastically reduce the chances of abrasion as well as limiting the risk of bacterial infections.
Territoriality does extend to their own kind, and so housing should be spacious if you intend on keeping more than one (although good luck in finding multiples). Despite this, they do fare better when kept with others of their own species, and so multiples should be sought where possible (and where budgets allow). An individual fish’s territory can vary greatly, some content with just a few private inches around them, others with a keener eye for starting trouble. Sparring, where it occurs, takes the form of side-by-side wrestling, with mouths agape or locked (with conspecifics) or lunging and charging (with allospecifics).
Did you know?
The long dorsal fin of a maassi loach contains anywhere up to 74 individual rays.