Use of Lasers in Controlling Pest Algae and Corals

[CalmSeasQuest]

I've been doing some research on the use of Laser light in eradicating and/or controlling certain pests frequent in marine aquaria. These include,

• Aiptasia / Mojano
• Blue/Green Algae including Valonia and Bryopsis
• Xenia
• GSP
• Virtually any other unwanted pests such as vermetid snails, predatory crabs...

In theory, it should be a simply process to eliminate any unwanted life from an aquarium, and easily prune others (think of it as a lawn edger for an area of Xenia or GSP.) I'm also curious about the possibility of using Laser to "cauterize" part of a coral subject to RTN. It might also work well for laser-fragging soft corals such as Z&Ps as it could be done while the coral was still in the water.
The most common laser pointers (< 3mW) do not generate anywhere near enough energy to be effective. Higher power lasers are now available that can emit enough energy to instantly "boil" the targeted pest, while avoiding damage to adjecent corals. The primary challenges with this approach,

• Cost - Higher power lasers are expensive.
• Safety - Eye protection is an absolute nesessity as intant blindness is possible should the beam (or potentially a reflection) strike your eye.
• Legality - There are FDA imposed restrictions on the sale of Class IV lasers (<50mW) that make them difficult (read expensive) to acquire.
• Risk to livestock - Caution will have to be mainted to prevent fish from being struck by the laser. At very high power settings, even viewing the point being lased can result in damage to their eyesight.

I've ordered the components to build a 1800mW / 445nm laser to test the above theories and develop effective practices. Here's what the components look like (you can't purchase pre-built due to FDA regs)...



The next challenge is safety (mine as well as that of the livestock.) At this power output, blinding could be instantaneous if shined in ones eye (including a reflection of the beam.) Even looking at the beam endpoint unprotected is dangerous. Safety goggles provide user/viewer protection. I'm still working on a shield to prevent injury to livestock. This idea was suggested by Lotus-Darkrose, a user in the Laser Pointer forums - albeit a bit difficult to deploy

[CalmSeasQuest]

I received and assembled the laser and waited for the batteries to charge (about 5 hours.) This model is 1800mW and generates a 445nm beam (beam is blue in color.) It has a 60 seconds maximum duty cycle and then requires a 120 second cooling time. I purchased a Pelican case and lock to prevent any unintentional access.





The second laser shown is a lower output <3mW laser with a 532nm beam (green.) This will be affixed to the main laser used for targeting and to test if any reflections will occur. The spectrum is important as the safety glasses block virtually all light in the 190-445nm range, making it almost impossible to see any reflections from the main laser. The green color beam of the targeting laser is easily viewable with the safety glasses on. Targeting with the low power laser is also important due to how quickly the main laser damages anything it touches. You would not want to hit a prized coral for even a second.

I've only had a time to conduct a few tests as I want to complete fabricating a shield to protect the livestock before continuing. Also, more time will be needed to fully determine the impact and to see if anything re-grows – but here is what I've observed so far…

Safety observations…This thing is scary-powerful. You have to be very careful.

• An 1800mW laser beam is both terrifying and amazing. I used a cardboard box to initially set the lens focus. The very instant the end point was focused, it began cutting through the box. In just a couple seconds the beam had completely burned through the cardboard.
• The Eagle Pair safety glasses do a great job of blocking light in the 190-540nm spectrum – All that is visible is an orange, pinpoint glow at the beam endpoint. Reflections are very difficult to see. This poses an additional risk and underscores the importance of first targeting with a low power laser (in a spectrum that can be seen while wearing the safety glasses) to test for dangerous reflections. It's also important to note that the glasses are designed to prevent against stray, reflected laser light – they are not designed to protect against a beam hitting you directly in the eye. After seeing the power of this, I shudder to think what would happen to your eye.
• Caution is advised is determining the angle at which you lase through the glass or acrylic. You have to be careful not to use the laser perfectly perpendicular to the glass/acrylic as unseen reflections will result in lasing your hand. Even the reflection is quite painful and feels like being stuck with a thousand needles. I now wear a long sleeve shirt and nitrile gloves when using the laser as another precaution.
• I have real concerns about any fish viewing the beam endpoint. Thus far, I've only used the laser in areas where no fish were present until I can fabricate a shield. I would NOT use this without a method to prevent livestock from viewing the beam end-point.
• Even after extended laser sessions with the beam in the same spot, I detected no temperature increase in either glass or acrylic. I made sure all panes were clean. As far as impact to the tank itself - I believe it to be completely safe for use from outside an aquarium.
• I've found it to be more effective if all water movement in the tank is stopped during laser sessions. The minimizes cooling keeps the targets still.
• I've ordered a second pair of safety glasses (~$50) to enable an observer to photograph and video the process. Without eye protection, I would not allow anyone (or any pet) anywhere near the room with an active laser.

Early Results

Wow… there is no doubt in my mind that this is an effective method to kill virtually ANYTHING in an aquarium. The immediate results vary based on the type of target. So far I've tried the following,

• Aiptasia – Highly effective. Within seconds, you can clearly hear a “sizzling” sound as they literally begin to boil – often following by a “pop” as they explode. They try and retreat as soon as the laser hits them. Assuming you have a clear shot at the hole – this only increased the lasers effectiveness as you're able to focus all the energy in a single spot (as opposed to lasing the fully opened Aiptasia. I will be very surprised if any of the Aiptasia targeted return. Time to total kill - <10 seconds.
• Green Star Polyps – Highly effective. Within in seconds they are toast. They burn very quickly.
• Xenia – Effective. Killing Xenia does to take longer than the Aiptasia – I'd estimate about 30 seconds. This may be due to their lighter color. It seems best to focus on the base of the polyp often resulting in a popping noise. Time will tell if they return.
• Mojano – I dont' have any Mojano in any of my tanks, but I see no reason why the results would be much different. It may take slightly longer to kill larger specimens, but the end result should be the same…death by LASER.
• Valonia – Too soon to tell. The laser quickly cuts directly though both walls of any Valonia bubble but more time will be needed to see if this actually kills the bubble.
• Miscellaneous Algaes – Too soon to tell. When lasered, virtually everything living begins to pop and smoke. It's amazing how clearly you can hear the sizzling sound. It would take a lot of time to destroy large patches of algae, but I believe it is possible.
• Cyano – Highly Effective. A quick pass makes Cyano disappear. It works although I think there are more effective means to combat Cyano.

I'll follow up with before/after photos and video once I receive a second pair of safety glasses for an observer to film and with updates as to if any of the targeted pests regrew.

[secretreefer]

wow. this is getting high tech. thanks for sharing. i got me a laser at home too.

[Reef keeper]

very cool, following!

[-Logzor]

Wow this is too awesome. How much is a death-laser gona run me?

Looking forward to hearing results on the effects it has on the bubble algae.

[Wy Renegade]

Interesting research here, so following along.

[subielover]

Freakin laser beams on their heads!

[florida reef]

Freakin laser beams on their heads!

First thing I thought also!
This is awesome.

[revhtree]

Fantastic write up! Thank you for sharing!

[chindo]

This sounds very interesting... I got a lot of manjos in my 180g tank and was thinking of tearing it down and starting over but this may be worth it even at the 400 dollar range