THE NATURAL WAY TO FIGHT ALGAE is to use floating plants (which provide shade over the water, and they absorb nitrates and phosphates in the water which are the leading nutrients that algae consumes) and submerged plants (because submerged plants also consume nitrates and phosphates in the water, however, string algae will grow on your submerged plants if the sunlight is overwhelming, so if this is the case then you want plants that shade). The BEST chemical way to competite with algae in MY experience (and I have lots of experience) is to use a chemical called Green Clean, keep in mind this is not a preventative and it IS safe for fish, frogs, tadpoles, and snails (as long as you don't apply the powder directly on the frogs or tadpoles slimmy skin). Green Clean kills algae instantly, however, this chemical is expensive and we do not sell it. The next chemical I'd recommend is AlgaeFix, it takes a couple weeks to work (in my experience) and it's a third of the price of Green Clean. A product called Microbe-Lift is a good algae preventative, it's basically bacteria that eats algae spores (You need to kill the algae before you use this). The last chemical method is Barely Straw, which comes in straw, pellet, and liquid form. It releases enzymes to control the algae (we use enzymes in our body to break down food). This is a cost effective method and is similar to AlgaeFix as far as how long it takes to control the algae.