For better result, try to get the ADA Multi long bottom. Which contained 30 pcs and allow you to use more than a year. Please remember...a piece of Multi long bottom able to supply the neccessary nitrient to as wide as 1.5 square feet. And you only need to insert again after 3-4 months. So, if your tank is 2ft tank. 1 piece for 4 months for example and 3 pieces for a year. And you have 30 pcs, which mean you can use for 10 years. (if you are able to just maintain the 2ft for 10 years.)