Green Star Polyps Not Opening [7 Reasons Explained]

It’s very frustrating if it’s been 2 weeks and your green star polyps are still not opening. You will be very much curious to find out the reason. 

Why exactly are your green star polyps not opening?

There can be many reasons why your green star polyps are not opening. It can be because of water flow, lighting, or even placement.

Water temperature also affects their lifestyle and may hurt them if wrong. Finally, you have to maintain several water parameters to keep them healthy.

You might still be dizzy about this matter. To clear yourself out, read along with the whole article.

How Do You Notice Green Star Polyps Not Opening? 

Green star polyps are fast-growing and can handle less ideal water conditions. They are easy foraging corals to maintain compared to frogspawn corals.

Frogspawn corals may die easily, but green stars are more likely to survive. That’s why so many people are fond of them. 

These corals are vibrant and love to flow in the water most of the time.

Green star polyps have neon green or pale green grass. It’s like tentacles flowing in the water when they are fully open. 

When they are closed, they form a purple mat. And you can’t notice the green tentacles. Green star polyps generally open between 1 and 2 weeks.

Why Are Green Star Polyps Not Opening? 

There can be several reasons that may cause your green stars not to open. Some are serious. Some aren’t. That’s why we’ve listed all of them. 

We’ve also provided the necessary steps that need to be taken. So, sit back, relax and go through the reasons individually. 

Reason 1: Inadequate Water Flow Can Make Polyps Shut Down

Too much or too little water flow can lead to a coral not opening. They love water movement, either pulsing or variable flow rates. 

Constant water flow pointed to the coral can prevent green star polyps from opening. It can also hurt several other characteristics of a coral polyp

Solution: Add A Powerhead In Your Aquarium 

Adding a powerhead will solve your flow problem super easily. But you should avoid pointing the water to the coral. 

Because they can’t handle too much water flow. Green star polyps like moderate to slightly high water movement. 

Always point the water to the front glass. That means the powerhead will flow the water from the tank’s back and the front glass. 

Reason 2: Inadequate Lighting May Harm Them Physically 

Another reason that green star polyps won’t open is for lighting. This coral prefers low to moderate lighting.

Lighting is necessary for their survival. Without this, they won’t be able to make food easily. 

Solution: Ensure A Proper Lighting System

Make sure to place them in a tank with low to moderate light. The recommended lighting for them is between 50-200+ PAR

Green star polyps will do just fine in an actinic blue light. They look fantastic under acting lighting.

Unlike most bulbs, Biocube 32 lights can be upgraded. We strongly recommend these bulbs. 

Reason 3: Bad Placement In The Tank Cause Sudden Death

Placement is necessary for green stars. If you place it under too much light, it can be a problem.

High water flow will also hurt it, but we’ve mentioned that already. 

Solution: Place The Green Star Polyps In Lower-Middle Section

To ensure good health, you must place them in the right place. For green star polyps, lower-middle sections are the best. 

This area always has moderate water flow and lighting. They also love to sit on the top of the rock. 

Reason 4: Wrong Temperature Jeopardizes Their Lifestyle

No marine creatures survive the wrong temperatures. If the water temperature is too high, green star polyps may die. 

They aren’t the only creature that has this problem. Birdsnest coral may turn white if the temperatures don’t suit them. 

Solution: Maintain A Moderate Water Temperature 

Green star polyps prefer a moderate temperature. That’s where they bloom the most. If your green stars aren’t opening, it can be a major reason. 

The recommended temperature for green star polyps is 78 to 79 Fahrenheit. Make sure to set the temperature around this value. 

Having an aquarium thermometer can help you with this. Get any of these you like more, and start checking those temperatures! 

Reason 5: Bad Water Parameters Can Hurt Them Severely

Maintaining good water is a must. You can’t compromise this option. Bad water may cause them to starve and die. 

Solution: Maintain Optimal Water Parameters 

Green star polyps only like a specific amount of salt, magnesium, and calcium. This can be a little confusing so we’ve made you a list. 

Here’s what you’re looking for-

Water Parameters  Optimal Range
Salinity 1.025 sg or 33 PPT
Alkalinity 8 to 12 dKH
Magnesium  1200 to 1300 PPM
Calcium 400 to 450 PPM
Water Hardness 8.1 to 8.4 pH

Make sure these levels are maintained at all times. They’re very crucial for your green star polyps to stay healthy!


Question: How long do green star polyps last out of water?

Answer: A green star polyp can last 30 minutes out of water. Sometimes they can last only 15 minutes. The healthy ones usually can stay 30 mins out of the water easily. 

Question: How do you clean green star polyps?

Answer: Soft brushes are super useful for cleaning them. Take them out and scrub them gently. This will get rid of dirt, sand, and other algae.

Question: Are green star polyps deadly?

Answer: Yes, green star polyps are toxic. They can release different chemicals that are harmful to others. That’s why don’t put other corals too close to them. 


That’s all from us. I hope you are now clear about green star polyps, not opening. 

One last tip before we go-

Make sure to maintain a distance from other fishes or harmful corals. Some corals can also alter the overall chemical level in the water. That’s why make sure to keep the levels in check. 

Finally, good luck with your green stars, and have a nice day!