I use cuddle bone in all my tanks to add calcium to the water, they might eat some but it will mostly be dissolve into the water column.
Discoloration in new shell
The pigments that determine the colour of the shell are mainly located in to organic outer layer (periostracum) of the shell. The speed at which a snail grows largely determines the thickness of the periostracum. At slow growth speeds, a relatively thick periostracum is formed, while a high growth speed results in a thin, more transparant periostracum. It's not difficult to imagine that a thicker periostracum also results in a more intense and darker colour of the shell. It also explains why wild caught snails are often darker than the ones raised in a home tank as the conditions in the wild are often less optimal and food is less available, which results in slow growth and darker snails. The same often applies to snails bought in a pet shop. These snails are often bred in large outside tanks, which cannot compete with the growth conditions of some hobby tanks.
Thin and fragile shell
The growth of the shell takes place in several stages. In the first stage a thin and soft organic layer (periostracum) is deposited by specialised cell near the shell opening (aperture). This is often very well visible in young snails. After the organic outer layer is ready, the snail deposits calcium carbonate crystals at the inside to strengthen the shell structure. It's at the latter stage (the calcium deposition) that problems can arise if the water quality is not suitable for snails. In practice this means water with a low pH (below 6.5) and low in calcium content. The snails are unable to create a strong shell in such cases and become vulnerable to shell damage, especially when the protecting outer layer has vanished with age (common in older snails of some species). It's therefore advisable to test the pH if one notice shell problems. For most apple snails a pH of 7 to 8 is optimal. A low pH can be easily corrected by adding calcium carbonate to the water. Most aquarium and pond shops sell special preparation to increase the pH and calcium concentration. Crushed or powdered marble or seashells, lime stone and eggs shells are an alternative for the do-it-yourself hobbyist. Before you raise the pH, make sure that the other inhabitants (fish) of the tanks/pond tolerate a pH of 7-8. Also never increase the pH too much at once (0.5/day max.).
Rough shell surface in new shell parts
The quality of the new shell material depends on several factors: the water quality, the food quality and availability, the temperature, the age of the snail and the general condition of the snail itself. A fast grow does not imply a regular and smooth shell, it can even be the opposite as a fast growing shell can become irregular due to a fast growth of the soft outer layer, while the calcification hasn't taken place yet, resulting in a malleated surface. In fact the most beautiful shells are the results of a regular, steady and uninterrupted growth. To achieve this in captivity, one needs to keep the water quality excellent all the year round (regular water changes), and the temperature should stay at room temperature for most of the year, and last but not least: the snails need regulary feeding. The latter factor, the food, does not imply large amount of food, but rather a decent amount at regular intervals. Despite all precautions and care, it can happen that a snail grow an irregular and rough shell.This is often the case in old snails that restart growing due to improved life conditions. There is not much that can be done, except a reduction in food as that slows down the speed of shell growth.
So what to do once a snail has gaping holes and or a detoriated shell surface?
First of all, check the water quality: is the pH at 7 or more? (keep it between 7-8). How about the water hardness? (keep the kH and GH high).
A good way to regulate the water quality is to add a source of calcium in the form of crushed egg shells, specialized preparated, crushed sea-shells, marble or something similar. Once you are sure that the water is well enough to halt further detoriation, one has to decide if the shell should be repaired or not. If the snail is active, one can assume that the snail does not suffer from the damage. In such case a repair should be rather considerd a protective measurement to prevent other snails from attacking the exposed tissues. If however, there are no possible tissue eaters like fish and snails around, or if the holes are that small that the tissue stays out or reach, one can choose to leave the situation like it is. The snail will calcify the vulnerable tissues anyway as reaction to the exposition to water.
If however, a large amount of shell is absent or if there is a real treat for the snail to become eaten alive, once can choose to repair the holes by glueing pieces of snail shell, eggs shells or even pieces of plastic over them. The best glue for this is medical superglue, although common household superglue will do as well, but is toxic until it's dried. In such case (household glue) one needs to make absolutely sure that the glue does not come in contact with the snail tissues. Pits and detoriated surfaces can be repaired by covering them with strong nail polish (make sure to use water resistant polish), epoxy resin or even better super glue. The latter dries quickly and even hardens more when in contact with water. More info about shell repair can be found on Pam's website. She has carried out several experiments with shell repair and has a good practical guide available.
Operculum detoriation: holes, loss of operculum
While the shell mainly consist of calcium, the operculum is build out of proteins, although the species from the genus Pila also have calcium deposits at the body side of the operculum. The operculum is much less vulnerable to detoriations, but if a snail is not well fed, it can occur, however, that the operculum is thin and even get's holes in it. In such case, there is not much that can be done besides taking good care of the snail. Also keep in mind that the operculum is not essential for an apple snail to survive in a common aquarium with no snail eating fish around. Beside the shape and the smoothness of the operculum, the attachement of the operculum to the back of the foot is a good indication of the well being (or not) of the snail. In normal situations the snail's tissues completely cover the inside/body side of the operculum. If the snail is not in optimal condition, this tissue is retracted and only the center of the opreculum is covered by snail tissue. In such cases one needs to check the water quality and make sure everything is allright. Old snails can show such tissue retraction as well, while it's not necessairly a real problem with them. After all, one can compare this with the retraction of gums/tissues around humans teeth if not taken weel care of.Occasionally, it does happen that the whole operculum is lost. This is not a life treatening for the snail itself, but it often indicates a real serious health problem in the snail, so be sure to check the water quality and be sure the snail isn't dead.
Courtesy of http://www.applesnail.net/content/va...il_disease.php