It’s a great skimmer. In my 45g with a medium bio load it keeps nutrients very well under control. Tuning it is pretty easy once you figure out what is changing the water chemistry. This skimmer is sensitive to particular additives and will go nuts until they are gone. I will dump the cup and replace water with fresh salt water mix. There’s “something” in the cup that is being skimmed out even when the water is clear. Within an hour the skimmer will then start skimming normally again. You can also try putting the skimmer on a timer so it stays off during broadcast feeding or adding chemicals that may be the source of your issues. For me it’s very rare this happens anymore as I know which are the problem.

I have this currently in my Fiji Cube 40 in my 40 breeder it fits perfectly, I had some issues with it, seems a lot of calcium builds up in the air tubes and affects the air flow to the skimmer. That is the only issue i had so far, besides for that it is a great skimmer for nano tanks.

I have this on a jbj rf65. 65 gal mixed reef. Took about a month to fully break in but this thing pulls such great crud out. Will produce a lot of bubbles until broke in. Relax, it’s worth it. My bioload is 4 fish and corals. I empty once a week, thick skimate. Highly recommend.

By FAR the most fickle piece of equipment on my tank. Absolute microbubble factory. Difficult to tune properly. God forbid you unplug it to clean it, because the settings you just had for airflow and waterline will be completely different. Took it apart once to clean the air hose out and now bubbles come out of the seams of the unit. My honest advice is look elsewhere, this thing is a headache and the hardest part about my tank for me right now.

I bought this skimmer because it fit into the overflow chamber of my Red Sea Reefer 170 and I'm glad I did. I've had it for 3 years now and it's a workhorse. Usually smaller skimmers (in my experience) aren't that effective, but this has consistently pulled out solid skimmate for years and I've never had to tune it. I did eventually upgrade to a Nyos, which I also love, when my tank got bigger, but I still use this all the time whenever I'm in a jam (ex: power outage -> run this to oxygenate).

I really like this skimmer's performance. It skims well and is very quiet. However, I can't seem to find the sweet spot (if there is one) where it will not produce tons of micro bubbles. They come out the bottom of the unit. I haven't tried wedging some sort of foam in the bottom to see if that works. The folks at Tunze claim that'll just be one more thing to clean. While the bubbles don't appear to be harmful -- they are a bit unsightly IMHO.

got this for my 40gal breeder and it is a great skimmer for smaller tanks.... I'm really only giving this 3 stars because of the packaging. By default the magnet is attached to install on a rimless tank, and to place it on a rimmed tank you have to add the spacer to the magnet attached, and the directions say you need to use a screwdriver to pry it apart but it is definitely not as easy as I thought. I ended up bending the plastic tab holding the magnet in and ended up having to use an epoxy to glue the spacer back on. If it came with the magnet unattached it would have gotten 5 out of 5 stars from me.

Been using this for a month and keep getting micro bubbles coming out of the back of the skimmer and down the side where the seams meet ... not happy with this product . I have had the water level perfect and it is still happening.

it sucks the gunk out of the tank fast. I did the look and the performance. let it brake in get the level right. it takes a min to get things going but once you level it and get the air and it set up good this will quickly suck the gunk out.

This skimmer is running in my 20G Aquamedic Blenny. It works good if all conditions are perfect, such as level in the water, and no suction underneath the skimmer. In nano reefs without a sump like mine, the return pump will pull seriously on the output of the skimmer this can cause microbubbles in the water. Additionally the skimmer will not give enough foam a lot of times, this is because the inside air tubing (on the motor) is left too long in production. This creates a kink in the air line which limits airflow and thus less foam. Keep those two things in mind and this skimmer will work perfectly fine.

I had good hopes for this skimmer. Been using it for almost a year now, and I have to say - its horribly annoying to clean. The assembly is not intuitive and it always puzzles me on how to put together. The air hose slips off the pump really easily. I wish I would have picked a simpler style skimmer.

I've got this in my 30 gallon JBJ Rimless, and once you get it tuned in, it's a great skimmer. The magnets are a bit weak, but they still hold in place. Have yet to take it apart for cleaning, so I'm hoping it's not as bad as the others say. Still, probably one of the best nano skimmers out there.

Look for another skimmer unless you're a tunze fanboy or love fidgeting with your tank components. You will have to unplug it regularly (daily) to prevent clogging. If you ask for advice, you get vague answers like: raise or lower it, move the intake away from the back of the aquarium. Whatever...I've had this skimmer for a couple of years and can't wait to replace it. Way overpriced, too.

Overall this skimmer does a good job on my 20 gallon tank. It is very quiet, and collects a good amount of wet skimmate. On the negative side: It produces a lot of micro-bubbles. They come from the seams between the front plate and the body, and there doesn't seem to be anyway of stopping it. Also, the front plate can be difficult to remove for cleaning. You have to push in hard on the plastic tabs holding the front plate to the body, and every time I've done this I worry about breaking it. So far so good. But I have managed to cut myself multiple times as the front plate suddenly flies loose.

This is the first Tunze product that I've been really disappointed in. I'm surprised more people aren't talking about this issue in the reviews here. A simple Google search will show the issues with this skimmer. It is an absolute microbubble machine. The height adjustment of this skimmer is really finicky, and unless you have a quality ATO, pass on this skimmer. I checked that my pump and skimmer plate were installed correctly. That didn't work. I placed a foam insert on the bottom. That didn't work either. And unless there are surfactants in my water column that I don't know about, that shouldn't be the problem either. Given, I understand that these skimmers have a break in period, but at what cost when I can't even see what's in my tank due to the sheer amount of microbubbles. Furthermore, I've owned a plethora of skimmers in the past. A solitary break in period for this skimmer will NOT be enough to minimize the amount of microbubbles this thing produces. I'm not a believer that microbubbles cause any issues for fish or coral, however, when this skimmer created a large amount of them in my tank, two of my fish started to flash wildly against the sand bottom. This baffled me as it was the first time I've witnessed that. On a positive note, this skimmer seems to be made of decent quality materials, sans the extension pieces for the magnets. Those are very, VERY poorly made. The skimmer is also extremely quiet. You also won't get a nice dry skim out of this thing, but it did pull out a decent amount of gunk through a wet skim. Perhaps I got a bunk product, and you might have better luck with this skimmer than I did. I do believe that Tunze makes excellent products. Just not this one.

Although I do have a couple of complaints this skimmer still deserves 5 stars. 1: That air tube fell off during shipping but the excellent usa customer service handled it spot on. 2: collection cup is on the small side but the overall footprint is so small I wasn't expecting anything more. 3: that air control valve is just a simple screw that pinches the air tube when screwed in clockwise, simple and effective but I feel as if it will wear the integrity of the tube over time. Didn't require more than a day of break in time and this thing is producing some nasty (good) skimmate. I would buy this skimmer 10 times if I had to.

Bought this for a 40 gallon tank that didn't have a skimmer or an overflow. As a result, there was a surface slick of waste that was preventing light from penetrating to the bottom of the tank. After installing this skimmer, the surface slick was gone in about a week (skimmer took about three days to settle down) and the water is generally much clearer. Very happy with my purchase, great value for money. very silent, energy efficient, yet powerful and easy to clean. Will make this my go to skimmer for all tanks less than 50 gallons, especially if the tank doesn't have an overflow.

I bought a complete reef set up that came with a skimmer but alas, it was giant for this small 30gallon (sump included). I finally decided to throw the money at a new one and this one offered the perfect space saving to proper skimming ratio my tank needed. It fits nicely into my small sump and even leaves room for me to integrate a tiny refugium. To add to it, it skims great and my corals look happier than ever

I needed a protein skimmer that did a good job, wasn't too expensive, and was quiet due to the fact my tank is in my room. I was not disappointed.

I have been using this skimmer on my IM Nuvo 38. I switched from the IM Aqua Gadget skimmer I had on this tank. The Aqua Gadget skimmer required constant adjustments. This skimmer is working great, hasn't needed any adjustments after the initial setup and is quiet.

I have a 58 gallon Oceanic tank which is basically a tall 40 gallon footprint. Because of this size restriction I initially was running a BH1000 Reef Octopus hang on skimmer that just killed the aesthetic of the display portion of the tank, even if it was working great, it had to go. With the small size of the Tunze, I was able to put this in my sump which is otherwise devoid of space for a traditional skimmer. Although I am at the very top if not exceeding the size rating of this skimmer, I am running a relatively low nutrient system, but not ULNS by any means, with 6 fish and full CUC that is fed well daily. This skimmer is doing a great job all around. It took only about 2 days to break in fully, 3 days to tune, and pulls great skimmate consistently. The footprint compared to performance is amazing. The only minor complaints are in the reassembly after teardown and how short the breather line is. I wish it was set up for another 3-5 inches to place in comfortably out of my sump chamber. I could extend it, however they recommend against it, and I haven't had time to tinker yet.

Best nano protein skimmer I have ever purchased. I am using it on my JBJ 30g rimless and fits perfectly into the first chamber. Does an awesome job!

When I received the product I followed the instructions which were pretty straightforward and simple. Once I plugged it in nothing happened. I did a little research and found out it's very common for the hose disconnects from the pump in shipping. I took the device apart and sure enough that is what happened. I put back in the tank and it worked except I had a ton of micro bubbles in the tank. I did some more research on the position of the pump since the book doesn't explain how it should be positioned. I found a picture thT shows the pump attached to the front cover which made sense and worked. The pump has been operational for 2 weeks. I still have some bubbles but that is expected since it is in the tank. One problem I noticed out of the box was the magnet extenders are cheaply fastend to the body by clips. One clip arrived broken and the other ended up breaking so they are glued to the body now. The magnets are not as powerful as I expected so they do both old the unit super solid but it works.

This is on a JBJ 45 gallon rimless aquarium with the AIO sump on the back. Fits like a glove. Works amazingly.

I'm using this skimmer in my 60 gallon quarantine tank- works very well.

I have been in the reefing hobby for approximately 15 years and have used numerous products for my tanks. Tunze products have always been great for me. I recently bought a Fusion 40g and after much research for different brand skimmers I again chose Tunze. The Tunze 9004 skimmer I purchased has been excellent. I have read a lot of reviews from others about how the skimmer is difficult to reassemble after cleaning. I have not had this problem but maybe I have been lucky. This skimmer does a great job and my tank looks excellent. I have however had to make some small adjustments to the air valve during it's break in period but once tuned it is perfect. The advertisement for this skimmer states that it can handle aquariums in the 65g range but have not tried it personally so can't comment whether it can or can't. I know that there are more expensive brands that can be used for my size tank but chose Tunze instead and am glad I did. This skimmer is compact, virtually quiet during operation, and has the ability to handle a decent bioload as well. Does that mean you can house ten or fifteen 4" fish in a 30 or 40g tank when using this skimmer? In my opinion no and I don't think it should be tried. With common sense, a sensible amount of livestock, and frequent water changes this skimmer In my opinion will do everything it is advertised to do. Happy reefing!

I have a Innovative Marine 39g tank. The space in the back of the tank designed for skimmer and other gadgets is very tight and pretty hard to find a good right size skimmer. I tried ,Innovative Marine ghost skimmer medium size (that is so little it went completely under water) , Hydor nano skimmer medium size (did a horrible job), CPR bak-pak skimmer (my original skimmer) which was ok but the pump kept breaking and it was sooooo loud! In the end I decided to go with this skimmer and man am I so glad. It is super quiet! It seams to be doing its job (just install it so can't give much review about how good of a job it is doing). I get no micro bubbles (some reviews were saying it does produce micro bubbles). The magnets I would say are not to strong which many do complain about but if you are careful then you can work it out very well. In all I absolutely LOVE IT! The best investment so far! I wish the collection cup was a bit bigger though but not a big deal, I guess I can empty it more often.

I have the same complaint as many reviewing this online, and that is that it very flimsy and hard to get back together. The bubbles do come out all over too, but that doesn't make it less effective. Works great until you need to clean it. It took me 20 minutes to get the snaps to hold when putting it back together.