Check the listing for details. AquaChek Nitrate Test Strips (25 count). Condition: New. Listed at 16.99 USD. Tests for Nitrate and Nitrite (25 per bottle) - 641426 If you are seeing excess chlorine demand and algae growth check your Nitrate/Nitrite levels with AquaChek Nitrate/Nitrite Test Strips. DIRECTIONS: 1. Dip strip in water for 60 seconds. Do not shake off excess water. 2. Hold strip level with pad side up for 30 seconds. 3. Compare test strip to bottom pad color chart on the side of the bottle. 4. After 60 seconds, compare test strip to top pad color chart on the side of the bottle. SHIPPING: We will do our best to ship your order based on the shipping method selected, however in some cases, your shipping method may need to be modified to meet shipping requirements based on the carrier. Our current carriers used are UPS, FedEx and USPS. Please contact us directly through the "Contact Seller" link if you need UPS, FedEx or USPS specifically for your order.