Aquatic snails come in all shapes, sizes and colours. Their individual attractiveness is a matter of taste, but they certainly give an aquarium a more natural look, and perform some very useful functions to boot. Unfortunately, there are also some pitfalls that need to be avoided when keeping snails in a goldfish tank.

Most aquatic snails are tropical and should not be kept with goldfish.  It is particularly worth noting that apple snails are often sold as ideal tankmates for goldfish.  They are not, for two reasons: one, they are tropical snails that prefer the water temperature to be about 4 degrees celsius warmer than is healthy for goldfish; and two, goldfish will eat the ends of their antennae and eye stalks.

There are only two snail species that can be kept with goldfish, and they are the ramshorn snail and the pond snail.

The ramshorn snail has a shell in a flat coil shape that can be bright red, pink, blue, black, green, brown, orange or yellow.  It can also have stripes or spots in combinations of these colours.  The red and pink ramshorn snails have actually got very low pigment levels, allowing their unusually (for a snail) red blood show through.

The pond snail’s shell is more like the shape of a twisted cone, broad at the opening and ending in a point.  The variety of colours is not as wide as the ramshorn, but it can have a range of patterns and light and dark colours.

The main benefit of aquarium snails is their appetite for algae.  They will clean the glass, stones, ornaments, pumps and anything that has a surface algae will grow on.  This saves a lot of time and effort, and generally means that weekly water changes don’t need to be accompanied by scraping the glass and siphoning off the scrapings.

One thing that is very important to snails is the pH level of the water.  pH is a measure of the acidity or alkalinity of the water.  Although goldfish are happy enough with anything between pH6 and pH8, snails need it to be over pH7.  Anything below pH7 is acidic and will erode snails’ shells.

The biggest problem with aquarium snails is their capacity for breeding.  For every snail in a tank at the start of a year, 500 can be expected at the end of the year.

The solution to such a problem in most animal species would be to get either two males or two females to prevent breeding.  This won’t work with aquarium snails because both ramshorn and pond snails are hermaphrodites.  This means that each and every one of them has both male and female reproductive organs, and is therefore able to mate with any other snail of the same species.

The obvious solution to this problem would be to keep only one snail.  Unfortunately that won’t work either.  Both the ramshorn and the pond snail have an ability known as auto-fertilisation.  This means single snails can produce offspring without a breeding partner.

If this happened in an aquarium, all snails would be exact clones of the parent that auto-fertilized.  This is obviously not ideal, but in the wild it is a technique used by snails to quickly stock a body of water that has no snails in it.  Other unrelated snails will most likely arrive to mix in some new genes and prevent genetic problems.  Both species of snail can survive out of water, and do so to get to new ponds and lakes.

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