13 Watt PLS UVC Germicidal Replacement Bulb G23 Base Green water or single cell algae problems in Water Garden Ponds can be eradicated using a UV light clarifier. UV-C light germicidal Ultraviolet lamp or Ultraviolet UV Germicidal Bulbs help control the growth of algae. The increased water clarity improves fish viewing and it also improves the health of the fish. ? PLS Type H Glass ? 13W - 7" (180mm) ? Quartz Glass Construction ? Use in Pond Filters, Water Purifiers, Etc. ? For Best Results Change Every 6 Months or 8000 hours. We sell many UV Bulbs Online, check out our Store! Terms and Conditions. We use all approved forms for accepting payments. Sales Tax will be added to all shipments based on regulations. We always try to combine purchases, please contact us directly for a personal service. You will be notified on the day that your goods have been dispatched via e-mail with tracking which is used on all purchases. Please note that if there are any problems, contact us first via e-mail giving full details of any problem along with your user ID. We use USPS and UPS as our chosen carriers shipments to Hawaii, Alaska Puerto Rico may incur surcharges, contact will be made to advise before shipment at which point the order can be canceled if desired. Orders placed on Saturday/Sunday Public Holidays will be processed next working day. We pride ourselves on excellent feedback, if any part of the buying experience is not to your satisfaction, please contact us to rectify before leaving feedback. By committing to buy you are agreeing to the Terms Conditions stated above.