Quick guide to loaches

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Loaches make an interesting alternative to catfishes for the bottom of your aquarium. Dr Heok Hee Ng offers some advice on keeping loaches in your aquarium.

Bottom-dwelling fish can add interest and activity to the lower levels of your tank. When considering which ones to stock, catfishes are often prime candidates. However, they suffer from being a largely nocturnal group so some loaches are a viable daytime alternative.

Loaches are members of the order Cypriniformes, the world’s largest group of freshwater fishes, which makes them distant relatives of barbs, danios and minnows — and slightly more distant relatives of catfishes.

Prior to  recent taxonomic rearrangement, loaches were previously grouped in two families: the Cobitidae and the Balitoridae. Studies on the molecular phylogeny of loaches, as well as a reassessment of the morphological characters previously used to define the two families have, however, led to reclassification. Loaches are now divided into the Balitoridae, Botiidae, Cobitidae, Nemacheilidae and Vaillantellidae families. Here I’ll focus on Botiidae, a group perhaps the beginner will find most easily available.

Distribution

Botiid loaches are distributed from the Indus river drainage in Pakistan east to China and Japan and south to Sumatra and Borneo.  There are seven genera: Botia, Chromobotia, Leptobotia, Parabotia, Sinibotia, Syncrossus and Yasuhikotakia, of which Leptobotia, Parabotia and Sinibotia are from China and Japan and seldom encountered in the trade. 

Because of this, and the fact that they require cooler water, typically under 22°C/72°F, than most other botiids they are more difficult for the beginner.

The botiids featured are relatively easy to maintain, requiring slightly acidic to neutral water that is moderately cool as many species inhabit relatively swift-flowing rivers.  

As they typically inhabit such an oxygen-rich environment, botiids are more sensitive to higher water temperatures and the drop in dissolved oxygen. This also means they are sensitive to deteriorating conditions, so maintain regular water changes.

Botiids may not be as nocturnal as most catfishes, but a fair number are most active at dusk and even after lights out. It may be necessary to use subdued lighting for your tanks to enjoy these loaches at their best.

Botiids grub around a lot in the substrate, typically pushing their long snouts in to search for food. Therefore substrate should ideally consist of fine river sand, or fine rounded gravel. Like many bottom-dwelling fishes, botiids hide when inactive and ample hiding spaces should be provided.

These should be large, smooth rocks and/or driftwood, although purists argue that there is little sunken wood in the natural habitat of many botiids.

These fish will readily take live, frozen and dry food. They are omnivorous and many will also nibble on vegetables such as cucumber.

Although the molluscivorus reputation of some botiids precede them, don’t use them to clear snail infestations.

Many mollusc-eating loaches tend to be aggressive and as loaches are not specialist molluscivores will not tend to eat the larger, tough-shelled snails.

Botiids are best kept in a small group of three or more, as they school in the wild naturally. Plan your tank accordingly when keeping them because many grow to more than 15cm/6”.

Beware aggression

A number of botiid loaches are well known for aggression towards conspecifics and sometimes other tank mates.  These include all members of the genus Syncrossus and most members of the genus Yasuhikotakia. Aggression frequently involves biting, so keep only robust tank mates with these loaches or house them in a species tank.  

Be wary when handling these fish. All botiids possess a retractable spine below the eye, the suborbital spine, which the fish extends when stressed — as when removed from the water.

Botiids are also known to be good leapers, so have a tight-fitting cover on your tank.

Almost all botiid loaches undergo change in colour pattern as they grow and tracking those changes is one of the true joys of keeping them.

Popular species

Yoyo loach (Botia almorhae)

This relatively peaceful species is active day and night and reaches 17cm/6.7”. Mature males display a reddish snout and barbels. Water should be at pH 6.2–7.2, temperature at 22-27°C/72-81°F.

Dwarf chain loach (Yasuhikotakia sidthimunki)

This is critically endangered in the wild, but commercially bred fish are available. At a maximum 6cm/2.4”, this is the smallest botiid loach and excellent for community tanks. it is best kept in a group of six or more. Water should be pH 6.5–7.5, temperature at 24-28°C/75-82°F.

Zebra loach (Botia striata)

The zebra loach is also ideal for the community aquarium because of its gentle nature and, more importantly, because of its relatively smaller size to about 9cm/3.5”. Water should be at pH 6.5-7.5, temperature at 23-26°C/73-79°F.

Polka dot loach (Botia kubotai)

This species does best in a set-up with a current and also reaches 15cm/6”. Water should be at pH 6.5–7.5, temperature at 23-27°C/73-81°F.

Clown loach (Chromobotia macracanthus)

This is among the largest of the botiid species, to 30cm/11.8”, so plan your tank accordingly — especially since it is best to keep three or more individuals. Water should be at pH 6.2–7.0, temperature at 25-30°C/77-86°F.

Ask the expert

Dr Heok Hee Ng answers some of your common loach-related questions.

My loaches seem to spend a lot of their time lying on their sides at the bottom. Should I be worried?

Botiid loaches can lay on their sides in all manner of seemingly weird angles in a normal resting posture. If the fish is not breathing heavily or showing signs of stress, there is no cause for concern.

Why are clicking sounds coming from my loaches?

Botiid loaches are well known for this, particularly when showing displeasure with conspecifics. The manner in which these sounds are generated is unclear, although most researchers suspect some form of friction mechanism in the teeth and jaws is responsible.

My botiid loaches sometimes appear to lose their vibrant colours and appear more uniform in colour. Are they ill?

Some botiid loaches adopt a marked colour change when interacting with each other. This results in the fish becoming less contrasting in colour pattern and appears to happen when they are trying to establish dominance in the social hierarchy. This change is temporary and not cause for concern.

This item was first published in the October 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.