Should I worry about the snails in my substrate?

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Do you have cone-shaped snails living in your substrate? If so, how much of a pest are they? Matt Ford explains...

It sounds as though you have a colony of thiarid snails, probably Melanoides tuberculata (aka Red-rim melania, Malaysian burrowing/trumpet snail or simply MTS) or possibly Quilted melania, Tarebia granifera.

These are often referred to as aquarium pests since they can reproduce incredibly quickly when there’s a consistent excess of food about.

As you’ve seen, they spend most of their time in the substrate but do emerge occasionally, particularly at night.

They’re often said to be hermaphroditic, so possessing both male and female sexual organs, but in fact reproduce by parthenogenesis whereby females produce embryos which develop unfertilised and give birth to live, fully-formed young.

Males do exist, but in small numbers compared to females.

These snails are beneficial in the majority of aquaria since they eat detritus trapped in the substrate and their movement helps prevent anaerobic spots developing — particularly useful in planted set-ups.

They will not harm live plants, but do consume algae when they emerge at night. If their numbers rapidly increase its usually because of the overfeeding of fishes and/or insufficient cleaning of the substrate.

If you want to remove them don’t use a commercial product as most are harmful to shrimp and some fishes, or add a ‘snail-eating’ fish such as a botiid loach species. Most grow relatively large, exhibit complex social behaviour, meaning a group of eight or more is required and shouldn’t be relied on to eat snails.

Instead, reduce feeding and remove them manually at night or use a ‘snail trap’.

Incidentally, neither species is restricted to Malaysia. M. tuberculata is native to some parts of Africa, the eastern Mediterranean, India, South-East Asia, Malaysia, southern China, as far as the Ryuku Islands (Japan), and the Pacific islands, as far east as northern Australia and the New Hebrides.

T. granifera occurs naturally in India, Sri Lanka, South-East Asia, the Philippines, Taiwan and Japan, and can be told apart from M. tuberculata by the lack of reddish-brown spots on the shell.

Both species of snail are considered highly invasive and have been introduced into many countries where, in many cases, they have had a distinctly negative impact on the native gastropod populations.

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