Do not recommend them for anything bigger than 20l nano tank. The ones we sell It dissolve really fast. Within 5 mins in our demo fish tanks.
Pros and cons.
Pro - they are White, clean and easy to use. They also release micronutrients as they use these salts to bind the baking soda.
Con - they are not measured quantities. There is no way you can measure the quantity of co2 being released. The co2 spikes for 5 mins and then nothing!
Overall - for someone wanting a low tech nano they are good. For someone wanting a good lush tank with specialist plants such as ug or hc... these tablets are not good.
You can find CO2 tables on buyonine24.co.uk here