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Red Sea Protein Skimmer RSK-300


Starting at $30/mo with . Learn more

Item #: RS1230

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Red Sea Reefer RSK Protein Skimmers - Efficient - Quiet - Ergonomic

Red Sea Reefer Skimmers are powered by Sicce`s PSK Skimmer Pumps, a pump well known among hobbyists around the world for their efficient output.

The silent operation of the Reef Skimmers are attributed to the large air intake silencer, and the vibration dampening feet and connections.

The diffusion chamber of the Reefer Skimmers disperses microbubbles produced by the PSK skimmer pump evenly through the conical ergonomic body, while maintaining air and water flow.


  • FoamView window for foam regulation
  • Neck cleaner integration
  • Drain port connection with 3 foot draining hose
  • Graduated collection cup to monitor skimmate production
  • Highly effective air silencer
  • High volume reaction chamber
  • Sicce PSK Skimmer pump
  • Two positioning options for the skimmer pump
  • Precise gate valve for skimming control
  • Vibration reducing footing

RSK Ratings





SPS Tanks: 80 Gallons / 300 Liters 160 Gallons / 600 Liters 240 Gallons / 900 Liters
Mixed Reef Tanks: 160 Gallons / 600 Liters 320 Gallons / 1200 Liters 500 Gallons / 1800 Liters
Fish Only Tanks: 240 Gallons / 900 Liters 500 Gallons / 1800 Liters 740 Gallons / 2700 Liters


Sicce Pump Model: PSK-600 PSK-1000 PSK-1200
Air Flow (GPH/LPH): 130 / 500 195 / 750 235 / 900
Water Flow (GPH/LPH): 265 / 1000 400 / 1500 530 / 2000
Dimensions: 9.1L x 8.3"W x 21"H 10.2"L x 9.4"W x 22"H 11.4"L x 10.6"W x 23"H
Recommended Water Depth: 6-8" / 16-20cm 7-8" / 18-20cm 8-9" / 20-24cm

Compatibility Chart





Reefer Nano
Reefer 170
Reefer 250 V1
Reefer 250 V3 **
Reefer 350 V1 * *
Reefer 350 V3
Reefer XL 425 V1 * * *
Reefer XL 425 V3
Reefer 450 * *
Reefer XL 525 V1 * * *
Reefer XL 525 V3
Reefer XXL 625
Reefer XXL 750
Reefer Peninsula 500
Reefer Peninsula 650
Max E-170
Max E-260
Max S-400
Max S-500
Max S-650 ***
*Skimmer may need to be raised, **Refugium wall will need to be removed, ***Place in reactor chamber

Manufacturer information

With a dedicated team of scientists and other professionals, Red Sea is widely recognized as a leading innovator and manufacturer of quality products for aquarium hobbyists. Red Sea constantly strives to provide hobbyists of all levels with highly effective solution-driven products designed to make your fish-keeping experience as enjoyable and successful as possible.

The embodiment of Red Sea’s dedication to providing solutions for today’s reef-keepers is its range of MAX-NANO, MAX-E & MAX-S aquariums- The only choice for true Plug & Play™ coral reef aquariums, now featuring the very latest in LED lighting technology.

For advanced reef-keepers the Red Sea REEFER provides a great platform into which you can add your own selection of hardware. With its ultra-clear glass, ATO built-in, silent flow valve and superb quality of finish the REEFER sets the standard for those wishing to customize. REEFER is also available as a Deluxe version with LED lighting included.

Red Sea’s unique Reef Care Program (RCP) provides a comprehensive, safe and easy to use program for testing and supplementing within reef aquaria, and is perfectly complemented by Red Sea’s Coral Pro & Red Sea Salt’s, which has become the salt of choice for those seeking the very highest quality water quality for their coral reef aquariums. Both salts are made using a unique natural process which delivers unrivalled homogeneity and is perfect for delicate corals. Check your individual bucket of salt’s composition using Red Sea’s innovative new “MyBatch” software.

Whatever your aquatic needs, Red Sea delivers high quality innovative, solution based products.

4 Stars


Reviewed on
November 16, 2020

Yes, I would recommend this.

Awesome skimmer

Pros: Works great

Cons: Adjusting it for the load

I have been using it for about 11 months now and it has been working well it’s on my 125 gallon reef tank but you need to keep your eye on it it will over react to any small change and over skim but it is in my bedroom and it is very quiet and does a great job
At times it will need to be adjusted but that’s ok because I watch it on a daily basis

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Reviewed on
August 27, 2020

No, I would not recommend this.

Good Skimmer/Well Built/Intermittently Loud

Pros: Well Built/Sicce Pump/Neck Cleaner/Viewing window in skimmer cup

Cons: Can be loud/Needs Daily Adjustments

This is a nice skimmer extremely well built it is a beast. The neck cleaner is very nice and the "viewing" section of cup is very cool and works perfectly. Sicce pump has plenty of power and produces nice bubbles for nice dark smelly skimmate.

Now for the cons......the skimmer cup is very very difficult to remove..you have to rely on the neck cleaner and the extra large drain hose for daily maintenance. You would not want to struggle with removing the cup on daily basis. I have had problems with intermittent noise from the skimmer it gets really loud for periods of time at random. i contacted redsea they were extremely helpful but were unable to resolve the problem. They even sent me a new pump and well it still makes the noise off and on. I can deal with it and I am not sure if its a problem with every RSK 300 but it is definitely a issue with mine.

Its definitely not set and forget I use the recommended water level and have gone up to 8 inches down to 6 and I still find myself making daily adjustments. It also took nearly 3 weeks to break in ....

Would I buy this skmmer again?? I would have to say NO but issue is not bad enough for me to purchase a different skimmer.

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Reviewed on
July 03, 2020

Yes, I would recommend this.

Great build quality!

Pros: Easy to set up and maintain

Cons: None

I love the built in wiper for cleaning the neck. I wish they would offer a add on motor to automatically turn the wiper and clean the neck. For the price it's a good deal.

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Reviewed on
June 26, 2020

No, I would not recommend this.

It's hard to keep tuned more then a couple of days.

Pros: It's nice looking, Drain line is nice

Cons: Hard to keep producing skimmate, red sea instructions and support advise don't help.

I really wanted to like this skimmer more. The water level marking on mine was way off. It needed to be at least 2 more inches out of the water to get anything. I am constantly tinkering with the bubbles. It will be good for a couple days then either overflow or not do anything. I bought the Skimmer safety switch and it's saved me a few times.

I will be shopping for a replacement after a year of wasting time on it.

I contacted Red Sea to see if I was doing something wrong and they basically read the manual to me with a nice time if voice. It wasn't helpful to solve the inconstancy issues.

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Reviewed on
February 20, 2020

No, I would not recommend this.

Nice feaures but difficult to keep it operating correctly

Pros: easy to install, easy to use, and not too hard to take out and maintain. I love the drain hose as the best feature. It is quiet and I can barely hear it inside the cabinet. I cannot hear the motor, only the bubbles. Once you get used to taking it out and apart and cleaning, it isn't bad at all.

Cons: cannot keep the skimmate overflow consistent. I have wild swings in where the correct position of the gate valve needs to be. It will work correctly for a few days, and then the foam will drop very low, or it will go into massive overflow. I do not trust that I could go out of town for a business trip and feel confident that it will maintain itself consistently.

All in all, the design, ease of installation, and other features make it easy to start up. I really like the drain hose that allows me to drain the skimmate without having to take anything apart. I don't believe any other skimmer on the market has the drain hose.

This skimmer operated well for the first 6-8 months. I could maintain skimmate such that I needed to empty about every 3 days, like clockwork without having to adjust the gate valve - set it and forget it.
Now, getting the right adjustment with the gate valve is inconsistent and I have wild swings from underskimming to overskimming. At first, I had a very clear mark on where the gate valve should be which would produce skimmate on a consistent level. Now, I cannot find a consistent spot. Sometimes I have to open the gate valve nearly completely open to get foam to overflow. Sometimes I can get the right adjustment and it will work for a few days, and then the foam level drops and I have to continue to open the valve bit by bit until I can get foam back up. Sometimes I have to have it nearly all the way open and it will operate correctly for a day, and then it begins to flood over and dump back into the sump. Sometimes I can have it operating correctly for 3-4 days with gate valve halfway open, and then it begins to overflow and fill the cup in a matter of minutes. I cannot find and keep an adjustment that makes it work consistently. I am constantly having to tweak the gate valve by tiny increments up or down. Its either working correctly, I can't get foam to rise, or it is in massive overflow causing skimmate to flow back into the sump. I have to monitor it several times per day. There is no 'sweet spot' that I can find that will consistently produce skimmate at the right level, day in and day out. It worked fine for over 6 months, and now I have to monitor it daily.

Was this review helpful? 1 0


Reviewed on
December 06, 2019

No, I would not recommend this.

For the price not the best

Pros: Easy to drain

Cons: Too big, doesn’t skim correctly, too hard to take apart

Pretty easy to install, very big skimmer. Needs to be lifted out of the water a little in order to work. Very hard finding the perfect balance and flow for skimmer to work properly. Defiantly not the easiest to take apart and clean. For the price I would not purchase this again.

Was this review helpful? 0 2


Reviewed on
September 10, 2019

Yes, I would recommend this.

Easy to Setup

Pros: Easy set up and cleanup with easy tuning.

Cons: None so far.

I bought this a couple of months ago and finally set it up a few days ago. Although I haven't seen it work for long I will say it was easy to set up and it is ultra-quiet. The instructions were simple to follow. The squeegee feature is very cool and the tube with the valve to drain the skimmate is a time saver. So far this is a great new toy.

Was this review helpful? 1 0


Reviewed on
May 22, 2019

Yes, I would recommend this.

Red Sea 300

Pros: It’s very quiet. Produces a fine bubble. Has some cool features that do work

Cons: Seems like the plastic they used could have been a bit thicker on some parts. Even though I really don’t think it effects it’s performance..

Good features, build quality is decent. It’s not exactly built like a tank. The plastic could be a tad bit thicker. However it’s a nice skimmer and priced accordingly. I will say it’s almost completely silent. Can’t hear the pump or air intake. Once I have it running for awhile I’ll update the review. I’m definitely happy with the purchase so far.

Was this review helpful? 7 0


Reviewed on
May 05, 2019

Yes, I would recommend this.

RSK-300 Protein Skimmer

Pros: Good material quality. Like the cup dasher for cleaning out the neck.

Cons: Quality control to make sure all parts were included in the box needs improvement.

The skimmer looks to be very well built and very good material quality. The reason I gave it 4 stars is because the rubber foot and rubber connector from the pump and skimmer were mot included in the box. Hence, the skimmer is unusable. Called Marine Depot and they got on it right away and called Red Sea. Received an email from MD on Monday letting me know Red Sea Would Mail the rubber package ASAP.

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