# Affiliate disclosure Some links in our guides go to stores such as Amazon. If you buy through them, we may earn a small commission at no extra cost to you. It helps keep the calculators and guides free. We only link products we would use in our own tanks: test kits, water conditioner, filters, heaters. A commission never changes what a calculator tells you, and every recommendation stands on its own. Affiliate links are marked "What you need" and open in a new tab. As an Amazon Associate, TankCoach earns from qualifying purchases. Questions: [[email protected]](mailto:[email protected]).