HTH Super Extended Algae Guard 90 Day Algaecide

by HTH
Starting at$2949
Free Shipping*

Members get Free Shipping & 5% Rewards back for only $19.95/yr Learn More

Free Shipping on All Orders
Never Pay Extra
5% Rewards Back
Earn on Every Purchase
Rewards for Writing Reviews
Up to $20 for Each Product
Free, No-Hassle Returns
On Thousands of Select Items
5% Dining Rewards
Get Paid to go out Tonight
Free Stock Trades
Powered by Muriel Siebert & Co., Inc.
Add Club O Gold for $19.95/yr
Club O is FREE for Military, Teachers, Students, and First Responders
ITEM# 21779604
  • Delivery Estimate

    Select a Product Option to view shipping

      **Delivery date is approximate and not guaranteed. Estimates include processing and shipping times, and are only available in US (excluding APO/FPO and PO Box addresses). Final shipping costs are available at checkout.

    • Warranty
      Included: None
    • Notifications

      Receive product notifications for this item, and also receive other email-exclusive savings.

    Love this item?

    Save it to a list so you can find it anytime!


    something went wrong.

    Please refresh the page and try again.


    ITEM#: 21779604

    HTH Super Extended Algae Guard should be used to kill and prevent green, black, and mustard algae. One single treatment lasts three months. For a preventative dosage use 16 ounces per 10,000 gallons every three months. If you have visible algae growth use 16 ounces per 10,000 gallons. If you have a serve algae issue use 32 ounces per 10,000 gallons, once the sever issue has been controlled continue with maintenance doses.


    Color White
    Set Includes 1, 2, 4, 6
    Dimensions 3 x 6 x 10
    Warranty None
    Model Number 66514
    Country of Origin United States
    • Most Recent

    • Verified Purchase

      This user earned $2.00 in rewards for writing this review.Learn More

      So we had a very hard rail and I purchase 2 bottles of this stull which really is overkill as one bottle should have corrected the issue. Pure junk. This did not do a single thing for our pool. Still cloudy as ever, clean but cloudy. I have used this stuff in the past and has worked perfectly. This was my firm time going through Amazon for it and I don't know if it expired or what the problems but the stuff is not cheap and this last round produced 0% fix for our pool.

      Read More
    • Verified Purchase
      Option: 1-Pack

      Worked wonderful in the pool

      Read More
    • Good Product
      Verified Purchase
      Option: 2-Pack

      This user earned $2.00 in rewards for writing this review.Learn More

      I have used this product many times and have been happy with the results. It is very concentrated and last quite a long time. It is the same product I can buy at the big box retailers but Overstock has a better price and it is much easier than a trip to the store , which is often out of stock.

      Read More
    • Verified Purchase
      Option: 2-Pack

      Read More

    Questions & Answers

    Yay! Be the first to ask a question about this product.

    Shipping & Returns

    Contact Information


    Usually leaves our warehouse in 1-2 business days. *

    Shipping Information:

    Our standard shipping method is ground shipping. We also offer expedited shipping for most items. Your final shipping cost and estimated delivery timeframe will be available at checkout.
    Standard shipping details
    Expedited shipping details

    Standard Return Policy:

    Items must be returned in new or unused condition and contain all original materials included with the shipment. For the return policy on a Marketplace item, please refer to the Seller’s individual policy, located on the product page by clicking on the Seller name. More Details

    FINAL SALE EXCLUSION: Items marked as FINAL SALE are not returnable unless the problem you experience is the result of our error.

    For your protection, all orders are screened for security purposes. If your order is selected for review, our Loss Prevention Team may contact you by phone or email. There may be a two business day delay to process your order.

    ** Most Oversize orders are delivered within 1-4 weeks. Some orders may take 6 weeks to be delivered.