murky green swimming pool image

So you’ve just pulled off the pool cover and the water looks… well, not exactly how you left it. The internet has a variety of (sometimes questionable) suggestions for how to take your water from green to a sparkling, swim-worthy blue, which is why we’ve gone straight to the source: Our on-staff chemists. Here, we’ll give you the info you’ve been looking for including the list of pool products you’ll NEED, other pool products that may HELP, and in what order to apply them to your swimming pool for the best, fastest clear water results.

Keep in mind, getting your pool clean and clear after opening can take a few days. It could even take you up to a week depending on the condition of your pool water and the efficiency of your filter. So don’t worry – we’re here to help; let’s get started!

Shopping List for Pool Opening

HTH® Cal-hypo Pool Shock Treatment

HTH® Algae Guard

HTH® Chlorinating Tablets

HTH® Multi-purpose 6-way Test Strips

Balancers (HTH® Pre-measured Water Soluble Pods™ Alkalinity Up,  HTH® Pre-measured Water Soluble Pods™ pH Up,  HTH® pH Down,  HTH® Pre-measured Water Soluble Pods™ Calcium Hardness Up,  HTH® Pre-measured Water Soluble Pods™ Stabilizer – check your test strip to determine exactly which balancers you’ll need)

HTH® Drop Out Flocculant or HTH® Clarifier (Optional / As Needed)

HTH® Metal and Stain Defense (Optional / As Needed)


Mission 1: Get rid of algae 

Step #1: Shock the pool water 

When you pull off the pool cover, there’s a good chance you’ll find algae has taken over you pool water during the off season. The first thing you’ll want to do is apply shock in the evening based on the volume of your pool. It’s important to know that there are different types of pool shock formulas; it’s helpful to use a cal-hypo shock product because it will not cause over-stabilization of your pool water (also called “chlorine lock” (which essentially means your chlorine works much slower and you may need to partially drain your pool and replace with fresh water). The shock treatment you use will raise the chlorine level in your pool enough to kill the algae. If the first round of shock doesn’t kill all the algae, you may have to apply another round of shock the next evening. Make sure you’ve killed all algae before moving on to the next step. 

Step #2: Remove dead algae from your pool 

After shocking your pool, you should see a really incredible difference overnight. BUT, you’ll also see a lot of dead algae in your pool that you’ll also want to vacuum out. If the algae is hanging on the water and it’s difficult to vacuum, that’s when you can try HTH® Drop Out flocculant. A flocculant attaches itself to debris and weighs it to the bottom so it’s easier to vacuum. Turn off your filter during this time to allow the flocculant to work and settle all the debris to the bottom. Even after flocculant and vacuuming, your pool water may still be cloudy. That’s because some particles are too small to get removed by your filter. If your water is blue but still cloudy, make sure you turn your filter back on and run it 24/7 and follow the instructions on the package to apply clarifier. Clarifiers are similar to flocculant but more effective with really tiny particles; they’re designed to attach themselves to the tiny particles making them big enough to get picked up by your filter. 


Mission 2: Keep that algae away! 

Step #1: Add HTH® chlorinating tablets 

Now, we want to prevent that algae from coming back, so you’ll need to immediately start your algae prevention routine. Take your chlorinating tablet and place it in a floater or in the skimmer. Your sun-protected chlorinating tablet can be applied in daylight, so once all algae is dead and removed from the pool, you’ll want to immediately get that chlorinating routine started. You’ll probably need to add chlorinating tablets every week, so some pool owners like to get a large supply of them at the beginning of the season. 

Step #2: Apply HTH® Algae Guard 

Wait twenty-four hours after applying shock to apply your algaecide – it’s important to choose a strong algaecide that kills and prevents green, yellow and black algae; make sure you apply the correct amount based on the volume of your pool. Note: HTH® Algae Guard doesn’t just help destroy algae, it helps prevent it. That’s why applying algaecide routinely every week BEFORE you see any signs of algae will help keep your pool clean. 

Mission 3: Swimmer comfort 

Step #1: Test Your Water 

Your algae is gone and you’ve already started to defend your pool from any algae coming back; now it’s time to balance your water. Testing and balancing your pool water is important because balanced water makes healthy swimming conditions and makes the water comfortable to swim in for you and your familyTo test your pool water, start by dipping your HTH® Multi-purpose 6-way test strip in the pool water, following the test strip instructions. Then, use the free HTH® Textstrip™ service to text a photo of your test strip to 484-123 to get free personalized pool recommendations in seconds – including the products your pool needs and exactly how much. If you don’t want to use the Textstrip™ program, you can download the Test to Swim app™ and upload a photo of your test strip, or compare the test strip to the color guide on the side of the package to determine your balancer levels. 

Step #2: Apply your balancers based on your test strip results 

Once you know your pool’s alkalinity, pH, and calcium hardness levels, you can apply the balancers you need. Applying these during the day is fine. 

Note: If you know you have hard water or your water has a lot of metal in it, you may see stains on your pool surface and equipment or experience discolored water. If that’s the case, apply a metal and stain defense to your pool water as part of your regular maintenance routine. 

Mission 4: MAINTAIN Your Beautiful Pool Water! 

Step #1: Plan your WEEKLY pool routine 

Now, let’s make everything you did worth it by keeping your pool clean and clear all summer by establishing your pool care routine. This helps ensure that bacteria, viruses and contaminants don’t have a chance to cause problems. 

Every week: 

  1. Test your water 
  1. Apply your balancers based on your pool test results 
  1. Apply a new chlorinating tablet every week (or as needed) 
  1. Apply your shock in the evening 
  1. Apply algaecide 24 hours after shock 

Step #2: Choose a weekly “POOL CARE DAY” and stick to it 

Make sure you stay on top of your pool water care every week (or more in extreme weather conditions or heavy use).  

As always, we’re here to help. If you have questions, contact our help line at 1-866-HTH-POOL or talk to our experts with our live chat!