Will this loach eat my fish?  

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A reader worries about her new stock being eaten. Bob Mehen advises.

Q: I have 180 l planted tank, which has been running for about 18 years. At the moment it contains a small group of Black mollies, a Siamese flying fox, and a Clown loach that is 18cm long and over 15 years old. I have not introduced any stock for many years, but I would now like to add a small shoal of fish — is there a danger that the Clown loach will eat them? I wonder if you could offer any suggestions, please?

CAROL SWAIN, VIA EMAIL

A: Bob replies: Clown loaches can occasionally take small fish, although this is also true of most species: if they can fit another fish in their mouth then sooner or later, they will try! But with careful choice of the species of new fish, I wouldn’t be unduly worried, especially if the loach is well fed. It’s worth mentioning that Clown loaches are sociable fish that do best in groups of five or more. That said, your tank is too small for those kinds of numbers, given that they can have an adult size of around 30cm. What you do need to be careful about is introducing pathogens into your established tank with any new fish you add. As you haven’t added anything to this tank for so long, take care to carefully examine new fish before purchase and ask about what quarantine procedures and treatments the store has in place for new stock. I’d advise you to set up a quarantine tank yourself at home to monitor the new fish for a few weeks and administer any treatments necessary without the risk of harming your existing stock.

With regards to shoaling choices to live alongside your current fish, then I would recommend deeper bodied, hardy tetra species such as the Lemon tetra, Hyphessobrycon pulchripinnis; Diamond tetra, Moenkhausia pittieri; or Red-eyed tetra, Moenkhausia sanctaefilomenae. These all grow into bulkier fish than other popular tetras such as Neons, so shouldn’t be as tempting if your loach does decide to take an interest.

Barbs might also be worth looking at, again due to their deeper bodies and robust nature. I’d steer clear of Tiger barbs, but the less belligerent Black ruby barb, Pethia nigrofasciata, would be a good fit, with the males showing striking colouration.