Please ID this snail stowaway
I bought a piece of decor with Microsorum attached for a temporary tank I have running. Later, I spotted this snail and would be grateful if you could identify it. There are two Assassin snails in the same tank too. ANNE DEMBOWSKI, EMAIL
NEALE REPLIES: What you have there is a Tadpole snail, either a Physella or Physa species. These are small, air-breathing freshwater snails, closely related to the big Lymnaea snails often seen in garden ponds.
Tadpole snails, or Bubble snails, are usually thought harmless. They feed mainly on algae, especially diatoms, and also on organic detritus scraped off solid surfaces. They might nibble on very tender plants, and will certainly go for dying leaves, but otherwise do little harm in planted tanks.
As with any snail, if conditions are favourable, with lots of algae and uneaten fish food, they may multiply quickly and become a nuisance.
Tadpole snails lay their eggs on the glass in jelly-like lumps a few millimetres across. Inexperienced aquarists may even mistake these for fish eggs! These lumps are easy to remove with an algae scraper.
Your Assassin snails will try to eat the Tadpole snails given half a chance, but they do have an interesting defence. When harassed, they grip the substrate firmly and thrash their shells about, dislodging, or at least surprising, their predators!