Some tips for controlling algae. This tips refer to the green algae, not the brown. Brown algae is caused by bacteria and is very differnt to get rid of.
1. Light control. Make sure the tank is not getting any direct sunlight (near a window etc..). If the lights are not on a timer try setting them on one so that there is no chance of them getting any extra light.
2. Nutrient control. Excess food and poop in the water is the main cause of algae blooms. You can eliminate this by either feeding in a seperate water filled containor, or removing any uneaten food immediately. Removing the poop immediately helps too. Both food and poop can be removed by either a fish net or a turkey baster.
3. A better filter. You will probably find that when you get your heavy duty canaster filter that some of the algae goes away.
4. A larger tank size. The more water there is the less the nutrients that algae feeds on will build up. How much of the 50gallon tub is filled with water? And how big is your turtle? If he is over about 4-5inches then even if the tub is filled completely it is too small and he is producing too many nutrients for your filters and water changes to keep up.
5. More frequent, smaller water changes. Changing more than 50% of the water at once is actually a pretty big set back. It restarts your nitrogen cycle and actually makes it easier for algae to grow. Try doing small (10-15%) water changes every other day until you can get a better filter system.
Try taking a sample of your water to a good tropical fish store, ideally a speciality store will be best as they have the most acurate test kits. A lot of places like Petco and other large chains use not very good quailty test kits that dont do acurate readings. Try to find a place that uses Sera test kits, or at least sells them so you can do it at home. Test the nitrates, ammonia, and the phosphates.
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