Fluval COB as Grow Light Review

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This review is for all of the people that have aquarium lights hanging around, and want to know if they work on house plants.

Fishkeeping is one of those hobbies that can result in having a lot of excess Stuff. Lights, heaters, filters, air stones…etc etc etc forever.

And you can’t chuck it out, because one day the filter will break, you’ll need an extra heater, or you’ll have to quickly set up a hospital tank, and you’ll need an extra set of everything.

(By the way, adding an air stone to a water propagation station is an EXCELLENT way to get roots to grow faster – the trick to propagation is to ALWAYS add oxygen)


No. of LEDS: 14

LUX is the amount of usable light for humans, PAR metres measure a spectral range including how many photons fall on the plants in 1 second within that spectral range (source).

Distance from lightPARLUX
Is this good? I have no idea.
  • Wattage: 6.5w
  • Lumens: 290l
  • Colour temperature: 9000k
  • Estimated life span: 50,000 hours (about 17 years, if you use the lights 8 hours a day).

Where to buy Fluval COB lights

I got mine from Amazon, but they don’t always have them in stock. This is a good thing I suppose – shows that they’re popular!

Fishkeeping is one of those hobbies that people just…abandon a LOT, so it’s always worth checking out Facebook marketplace and eBay for old stuff. These things are meant to last SEVENTEEN years, so buying secondhand is a great option, especially if you can snap up a bargain.

Can you use aquarium lights to grow house plants

Yes, you can.

I mean, they’re not designed for that purpose. the wavelengths aren’t as ideal as designated house plant grow lights BUT if you have them lying around collecting dust (or you see a bargain) they absolutely do the job.

I can’t find any information on this other than that…they’re what I use. My Fluval COBs kept my Hoya alive and actually growing for the past couple of winters, so I’m confident that they work well enough to be worth it.

How long should I leave my grow light on for?

It really depends on where your plants are.

I used to have my plants in a recessed corner of my living room that barely got any light, and I kept them on for about 8 hours a day.

At the moment my plant shelves are in my office (purely because it’s so much easier to grab and photograph them when I need to) and they get a bit more light (they’re about 7/8 feet from a west-facing window), so I only keep them on for about four hours a day – two in the morning, and two in the evening, usually when I’m working.

In summer, I don’t keep my grow lights on at all. My plants would probably grow bigger and faster if I did, but that just means extra work repotting (as well as increased energy usage).

The lights are cheap to run, but let’s not waste electricity if we don’t need to!

Advantages of Fluval COB


These lights are tiny, and take up waaaaay less space than my other goose neck-style ones. Here’s what they look like on my shelves:

Fluval COB as grow lights on plant shelves

They’re easy to adjust as well, and the newer models with the clamp are even more adjustable. Mine have an adhesive strip at the back (hence why they’re zip tied on) which is SUPER sticky but hard to remove. Probs why they move to the clamp design.

A lot of the more upmarket plant grow lights are square, which is fine if you’re arranging your plants in squares, but a lot of us use shelves like mine (according to my faultless research involving checking out people’s plant on Facebook) and that can result in a lot of, er, wasted (?) light.

I assume it’s because a lot of people spending money on grow lights are using it to grow weed vegetables, so they use grow tents and are more concerned about cramming a lot of plants into one place, rather than making them look aesthetically pleasing.

Easy to fit

As I mentioned, they now use a clamp. The issue with this is that it’s designed to clamp on the top of an aquarium, rather than to something thick and horizontal like a shelf.

This is one of the reasons I wouldn’t recommend running out and buying these lights especially for plants, but if you have them lying around (or can buy them cheap) you can zip tie them as I have.

Cheap to run

I can’t tell you exactly how much they cost to run, because not only do energy tariffs vary, but when I was gifted these, my boyfriend upgraded his aquarium lights, so there’s no way of telling how much they cost us to run.

That being said, lighting is a minor cost when it comes to running aquariums, compared to running heaters and filters.

I already had them

This is the no. 1 reason I love these lights. They work really well, but in all honestly, I don’t know if a fancy-pants ‘proper’ plant grow light would outperform it.

As I said before, I don’t desire enormous plants. I don’t have the space. I just want healthy ones, and the Fluval COB works really well. These lights cost around £50/60 apiece, and I inherited FOUR.

Waste not, want not, kids.

Long lasting

I mean, seventeen years is plenty.

At some point, I need to try out some fancy lights designed for plants, but at the moment, I’m happy with what I’ve got. When I get a house with a designated plant (and aquarium) room* I’ll get some (recs in the comments please), and review them.

*We don’t need space kids, so this is as opulent as it sounds.

Disadvantages of Fluval COB


It’s too expensive to buy at full price for house plants, as that £55ish would be better spent on a specific plant grow light. I haven’t tried any around that mark, but this one gets good reviews.


I COULD cram more plants under them, but I like my shelves to look pretty. Max is probably four (depending on size) – you could definitely do better for the price.

Two cover my Ikea Fjallbo shelves ok, but three would be perfect.

Really sticky adhesive backing

This isn’t an issue unless you buy an old set, but it’s SUPER STICKY.


Moving them around isn’t really practical (makes sense since they’re designed for aquarium use, and you don’t want them dropping in the tank and scaring the fish – though they are waterproof).

The clamp is better, but still not great for non-aquarium use. Zip ties solve the problem, but it’s not, like, perfect.

Would I recommend Fluval COBs for house plants?

I wouldn’t recommend that you specifically buy them. I wouldn’t – I just inherited them, and they work so so well for ME, someone that wants healthy, but fairly compact plants.

If you can pick them up cheap, then go ahead, but don’t buy them specifically for plants, as that’s not what they’re designed for.

What I look for in ideal grow lights

Cheap to run

LEDs are cheap to run, but a lot of the fancier grow lights have added extras, such as fans and control panels that cost more to run.

Not only does that increase the actual electricity cost, but it means that more things can go wrong. Complex control panels can often cost more to fix than it would be to just replace the light (source: one broke on the dishwasher at work last week).

Not too expensive

I thought they were expensive until I found out that the lights my boyfriend had upgraded to cost FIVE HUNDRED POUNDS.


He has no other hobbies and doesn’t go out, like, ever, so I can’t really complain, but I cannot fathom spending that much money on a light.


I know that the LEDs can last 17 years, but I want the whole unit to be durable. LEDS are no good if the casing is dropping apart.

Able to link together

At the moment I have four lights, each with an individual plug. They have connector thing in the middle of the wire, so I guess maybe you could fit them all to a single plug using a connecting cable, but that’s a bit complicated for me.

You can get some growlights (I assumed to cater for the veg-growing crowd) that all link together and connect to a single plug.

Being able to plug in my lights, laptop, AND charge my toothbrush simultaneously is the dream

Work for my plants

I just want them to grow.

Light is BY FAR the thing that has the biggest impact on plants. If you get the light sussed, your plant will be more forgiving of any watering or fertilising mishaps and will have more energy to fight off pests.

Alternatives/ recommendations for grow lights


These gooseneck types lights all over Amazon are fine. They’re not incredible, but they’ll keep your plants alive.

You don’t need the purple ones – the white ones are just as good, it’s just that blue and red diodes are cheaper for the manufacturer.


This type of light is next on my list. I love that they’re linkable, don’t love that they’re purple.

I don’t think they’re as effective as the square one I linked to previously, but they fit on my shelves.


The issue with the really fancy grow lights is that they’re predominantly for commercial use I worry that one of these would blind me if I bought one for my office (although it’d probs light my whole room AND run on one plug…).

The reviews though. People freaking love it. Am I convincing myself to get one???

Did I, unknownst to myself, write this entire article to try to convince myself to buy one mahoosive grow light???

Final thoughts

In short: old aquarium lights are great for growing plants, but not as great as designated plant grow lights. If you can find some cheap, they’ll work just fine, but if you want to treat yourself to some new lights, buy proper plants ones.

Caroline Cocker

Caroline is the founder and writer (and plant keeper) of Planet Houseplant

3 thoughts on “Fluval COB as Grow Light Review”

  1. What about using the Fluval Nano for house plants? I just got this idea and I’m not using the lights I have 3 of them from when i had fish tanks. But using them for the house and i Google searched it and came across your link for the fluval COB light.

  2. Definitely give them a go – whilst they won’t be up there with professional grow lights, they’ll be much better than most grow lights you could buy for an equivalent price. They provide great specs without being as bright/hot as professional grow lights, so your plants won’t dry out so quickly.

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