I have slightly acidic water for most of the year and it is tough on the snails. I use Cuttlebone and just let if float in the tank until it sinks shell part up. Then I stick it into the substrate like a surfboard in the sand on the beach. That way the water erodes the Cuttlebone (and it makes cool patterns so I don't always hide it in the back of the tank) and the snails seem to munch on it periodically.
Hikari Shrimp Cuisine and Crab Cuisine are what I give them regularly, mostly Crab Cuisine because it is about less than half the price of the Shrimp Cuisine. That has minerals to support shell formulation. They like it. I also think they like the Hikari Bottom Feeder wafers, in the orange-ish color accent package. so I will feed an extra wafer of that once in awhile to make sure they get some. They also get some blanched spinach and Kale occasionally, they are still learning to like it. I have started growing my own yearly.
They also liked some Kale that I over cooked in the microwave, (in a bowl with a little water) by mistake, and it dried out. I crunched it up into little bits and they raced for it, along with many other tank inhabitants!!!
