level. Common methods to reduce population include treating plants to prevent introduction, various manual methods of control, introducing the snail-eating animals listed earlier, and poisoning the snails. Soaking the plants in various chemicals may kill off the snails and their eggs. A 10-minute bath in a solution of 20 parts water to 1 part chlorine bleach has been suggested for hardier plants, followed by soaking in water containing a dechlorinating agent. A more gentle treatment calls for 5–10 tablespoons of alum to 1 gallon of water for 2–3 days. A safer alternative may be placing the plants in a quarantine tank, and adding snail poisons to that tank rather than the main show tank. Manual methods include baiting the snails with lettuce (run it under hot water first and leave overnight), cucumber slices, or food pellets. These may be left out in the open, and removed with their snails, or kept in some container, such as a film canister weighed down with a pebble, and containing holes drilled in it. Crushing the snails by hand as they appear can also effectively limit their population; most ramshorn shells are fragile enough that this is quite easily done. Introducing animals to control a snail population can require some thought. Other aquarium fish may not be compatible, and some larger adult snails may be too big to be eaten by smaller snail eating species. It may occasionally be necessary to crush a few snails manually so that the fish realize the snail can be eaten. Snail eating species also do not usually discriminate between different types of snails, although this is usually not much of a concern. Snail poisons are generally considered to be a last resort, as most of them are copper-based and are potentially toxic to plants and fish and particularly dangerous to other invertebrates. Even new safer chemicals that do not harm the other aquarium inhabitants may cause damage if large numbers of dead snails are allowed to decompose. For this reason, it is best to reduce the snail population by other means as much as possible before resorting to poisons, and to do frequent water changes afterwards. Some also recommend adding ammonium protection to the tank. Zeolite chips, and various liquid products such as amquel may help in this area. "Giant ramshorn" snails Totally unrelated to these ramshorn snails is the species Marisa cornuarietis, which is often sold at