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Juwel light units: maintenance and care

Juwel light units: why do they go wrong

How reliable are Juwel light units?

We sell thousands of Juwel light units and Juwel aquariums containing these lights every year. Our customers have units of all sizes, ranging from the older Juwel T8 units, which Juwel has now discontinued, to the more modern Juwel High Lite T5s, and the overall fault rate for both types is very low.

Juwel Light Unit

Juwel light units are really reliable in general and can go on for years without any problems. However, there are a couple of things that can cause them to stop working. Due to the popularity of Juwel aquariums and the volume we sell, they are also among our most frequently returned products and we get a few sent back every week. However, the vast majority aren’t actually faulty!


Why is my Juwel light unit not working?

We reckon that around 70-80% of all Juwel light units we see returned are actually fully functional – they just need new bulbs fitting. If you come home one day to find your Juwel light unit not working there’s a strong possibility it’s simply that the bulbs have blown.

Juwel light units typically contain two T5 or T8 fluorescent lamps, and if one or both of them blows – which they can do after 12 months or so – neither of the bulbs will light up. This leads the customer to believe the entire light unit is faulty, when really it’s just the fluorescent tube that’s blown.

The customer has to go to the hassle of calling us and booking a return, when there’s nothing technically wrong with the item at all. We need to test every unit returned to us – particularly given the high number of products returned which aren’t actually faulty. So customers can be without their light for no reason for a week or more. Although it doesn’t really cause any major problems for the livestock, this is an inconvenience most aquarium owners would rather be without.

Juwel Ballast

It’s also really expensive for us, since we cover all costs for the customer. We pay around £10 for the item to be collected from the customer, and £5 to return it, and need to employ specialist staff to handle the returns.


What else can be the cause of a faulty Juwel light?

There are two really common things. The first is simply that the fuse has blown in the plug. This is something that can happen to any electrical appliance and it’s easily fixed by non-electricians for under a pound, with no need to return the product to us.

The second is that the socket or extension that the light unit is plugged into has developed a fault. It’s really common for the returned Juwel light units, and other electrical appliances we get returned, to work instantly as soon as they’re plugged in, but for the customer to claim upon its return that it still doesn’t work, only later to find that it was their plug socket or extension cable which was at fault. As a result, we always recommend that customers plug the lamp into another socket they know to work to see whether it works in that.


Which replacement Juwel bulbs do I need for my unit?

Firstly, you need to make sure that you pick the right replacement bulbs for your Juwel light unit. Juwel aquariums all include Multilux lighting. In newer models these are generally Juwel High Lite light units, which take narrow Juwel T5 light tubes. In older models, and those at the bottom end of the Juwel range, they are Juwel T8 bulbs. It’s easy to tell the difference: Juwel T8 bulbs are 1″ in diameter, while Juwel T5 bulbs are 0.5″ in diameter.

Like other fluorescent bulbs, Juwel light bulbs are sold by wattage and length – you’ll need to know both to pick the right one for your Juwel aquarium.

The 55cm/24 Watt bulb will work in the Juwel Trigon 350, Juwel Delta 80 and Juwel Lido 100. The 60cm/24 Watt bulb is for the Juwel Lido 120. The 70cm/28 Watt bulb fits the Juwel Trigon 190, Juwel Delta 100 and Juwel Delta 300. While the 80cm/28 Watt bulb is for the Juwel Rio 125 and Juwel Panorama 80.

Of the larger bulbs, the 92cm/35 Watt fits only the Juwel Vision 180. The 100cm/45 Watt bulb fits the Rio 180, Panorama 100, Trigon 350 and Delta 300. The 120cm/54 Watt bulb fits this Juwel Rio 240, Juwel Rio 300 and Juwel Panorama 200, while the largest bulb, the 150cm/54 Watt fits either the Juwel Rio 400 or the Juwel Rio 450.

Juwel High Lite bulbs also come in several colours. The Juwel High Lite Day bulbs are bright lamps designed to stimulate plant growth in tropical freshwater or coldwater aquariums; Juwel High Lite Nature bulbs produce a warmer, less bright light also designed for plant growth; Juwel High Lite Colour bulbs help emphasise red and blue colours in fish, while Juwel High Lite Marine are designed for general marine aquarium use, and the Juwel High Lite Blue is an actinic blue light designed for corals and other photosynthetic inverts.


How do I pick the right replacement Juwel lighting?

If your unit is out of warranty and you are looking for replacement Juwel lighting you simply need to select the same replacement light unit as the one you already have. If you have an older Juwel aquarium, it’s also possible to upgrade to the newer Juwel High Lite T5 light unit, which will provide better lighting and a wider range of bulbs.

Juwel made its light bulbs a different length to the standard T5s used by other manufacturers, so you’ll need to buy official Juwel T5s to install in your unit. Standard T5 bulbs won’t fit.


How do I install new Juwel light bulbs?

It’s very easy to install new Juwel light bulbs. However, if you don’t install them correctly they may not light up and water could get into the light unit, which could damage it irrepairably. Juwel recommends that you always replace both bulbs at the same time, rather than just replacing one. This is a good idea, because it’s difficult to tell which bulb has blown since the unit won’t work with only one working bulb.

Juwel Lamp Replacement

Firstly, you’ll need to unplug the light unit from the mains to make it safe to work on. Don’t just switch it off, actually pull out the plug! Carefully unscrew the white lamp holder at each end and slide it along the tube. Then, carefully remove the tube by pulling it towards you. It sometimes takes a wiggle to get it out.

Juwel Lamp Pins

Slide off the end caps from the old tube, unbox the new tube and slide on the end caps. Align the pins on the end of the bulb with the holes in the lamp fitting, then push it into place until it clicks. If it doesn’t get seated properly there won’t be an electrical connection and the bulb won’t work. Slide the end caps down and firmly tighten them up.

Make sure your hands are dry, then plug the Juwel light unit back in and turn on the power. The bulbs should light up when the switch is turned on. If they don’t, double-check that you’ve replaced both bulbs (a single faulty bulb will cause the entire unit to stop working) and that the pins are correctly seated. If this doesn’t work, check the fuse and then the plug socket to make sure they’re not at fault.


How can I determine whether my Juwel light unit is faulty?

If your Juwel light unit is not working, here are the steps we’d recommend taking to ensure it’s faulty before sending it back for repair or replacement.

1. Re-install the bulbs

Juwel recommends that you first try re-seating the original bulbs if your unit fails to turn on. Unplug the unit from the mains and remove it from the aquarium. Unscrew the end caps and slide them along the bulb then carefully remove and reinstall each bulb, screw the caps back down and plug it in. If that doesn’t work, try step 2.

2. Install new Juwel light bulbs

The most common reason for a Juwel light unit to stop working is because one or both of the fluorescent tubes have blown. Try replacing these first, particularly if the bulbs are 12 months old. Darkening at the end of the bulb is a good sign that it’s on the way out…

3. Plug the Juwel light unit into another socket

Faulty plug sockets and extensions are another big problem. To confirm that the problem doesn’t lie with your plug socket or extension lead, plug the light unit into another socket that definitely works.

4. Change the fuse on your plug

Change the fuse in the plug of your Juwel light unit. Make sure you replace it carefully and use a fuse of the correct size.


What happens if the ballast fails?

The ballast in a Juwel light unit is inside the sealed part of the unit as it needs to be protected from water getting to it. If this part goes wrong, unfortunately the unit can’t be repaired and you’ll need to replace the entire unit. Water rarely gets inside Juwel light units, unless the user hasn’t installed the bulbs correctly and the waterproof seals at the ends of the bulbs aren’t fitted snugly.

When this happens the unit will usually just trip your circuit breaker, so tripping is generally a sign that the unit is wet due to incorrectly seated bulb seals.

There are some guides on fishkeeping forums which show how some users have cut open their Juwel light units with a Dremmel and replaced the ballast, however, although this may result in a functional light, it’s potentially dangerous and we highly recommend you do not attempt it!


How long are they guaranteed for?

Juwel light units are guaranteed for two years from the date of purchase. The guarantee only covers the unit itself, and not the bulbs which are disposable items (like the tyres on a car) and need replacing every 12 months or so. If the unit develops a fault within two years, and you’ve confirmed it’s definitely not the bulbs, the plug fuse or your socket or extension, you can return the unit to the place you purchased it from under warranty.


How do I return a faulty unit to you for repair or replacement?

Old Juwel Lamp

If you’ve tried fitting new Juwel light bulbs (the entire unit will fail to work if just one of the bulbs has blown), have fitted a new fuse, and have tested the light unit in a socket you know to work, please give us a call to arrange a return. We’ll check whether the item is in warranty and help you get it sorted.

We will cover the cost of collecting the light unit from you and the cost of returning it. You won’t even need to go to the Post Office as we’ll pay for the item to be picked up from your door. You will need to find a suitable box for your light unit and pack it very securely to prevent it being damaged in transit. You’ll also need to include a sheet of paper inside which explains what the fault is and who it was returned by.

There’s no need to affix a label to the box, since the courier will add a pre-printed label to the box when he collects the parcel from you. However, don’t forget to put your name and address on the outside so we know who the return is from.


How often should the bulbs be replaced?

The bulbs can continue to work for well over 12 months, but the useful light they emit starts to drop by the time they’re about a year old, so they become less useful for growing plants and corals, and some say they may even start to encourage the growth of algae. As a result, most experts recommend changing the bulbs every 12 months to keep the light spectrum and intensity produced at the optimum level.


  • james flurrie Posted 09/08/2013 at 11:34 pm | Permalink | Reply

    hi there i have a juwel monolux and the transformer broke in my tank lid so i took all the electrics out and put in another transformer from another tank but its not a juwel one and it works fine. but i would still rather have the proper transformer why do u not sell them? i cant afford to pay £120 for a whole unit.

    • Simon Keegan Posted 13/08/2013 at 8:44 am | Permalink

      Hi. Juwel do not sell them as all Juwel hoods are water tight and shouldn’t be accessed so they don’t sell these, only new lids. Give us a call if you need one.

  • Ross Waite Posted 02/09/2013 at 5:13 pm | Permalink | Reply

    Hiya, we have recently bought a second hand aqua one 400 tank and the front two lights work, the back two don’t. We have tried the front two lights as well as new lights in the back but still nothing. Any ideas if this is easily fixed? Or how much it would be for a new unit? Many thanks

    • Simon Keegan Posted 03/09/2013 at 4:23 pm | Permalink

      Hi. I’m afraid we don’t sell or deal with Aqua One but it sounds like a faulty light unit

  • angela Walton Posted 03/09/2013 at 10:41 am | Permalink | Reply

    Hi , I have a juwel panorama 200 and the problem I have with my lights is that when I switch them on both bulbs light but then flick off after about 20 seconds , is this the bulbs or the ballast ? Thanks .

    • Simon Keegan Posted 03/09/2013 at 4:22 pm | Permalink

      Hi. It sounds like a problem with the starter unit. That is an old tank (10 years old +) so will have a pre-electronic starter. You can replace these easily (B&Q etc)

  • Jason Posted 26/09/2013 at 7:57 pm | Permalink | Reply

    Hi there. I bought a new juwel unit less than a month ago and it has stopped working. I bought new bulbs and have changed the fuse but still no joy. I cant find a receipt either unff! Do you have any suggestions? Thanks

  • Stuart Bingham Posted 26/09/2013 at 8:31 pm | Permalink | Reply

    hi my t80 light unit lights for about 2 secs then goes out is it the bulbs? thanks

  • amanda Posted 30/09/2013 at 10:20 am | Permalink | Reply

    Hi my lights on.my jewel 190 come on then go straight back off is it the light unit ?

  • Elaine Posted 01/10/2013 at 2:02 pm | Permalink | Reply

    Hi, can the built in hood light in Juwel tanks withstand getting wet? Mine is getting splashed with water caused by using air pump/stone? Many Thanks

  • violet Posted 14/10/2013 at 10:43 am | Permalink | Reply

    Hi,i have trigon 190 with t8 bulbs,both bulbs went at same time,i thought just to replace bulbs,having done so the lights flicker on then off again,can you give me any indication as to what it could be,there is no water in the on or around the unit itself.i havent a clue what else to try apart from replacing the unit.thank you.

  • Tristan Posted 16/10/2013 at 1:56 pm | Permalink | Reply

    hello, i have a just replaced the bulbs as i thought they had gone one strip flickers for 1-2 sec then nothing at all with the new bulbs, if this is the starter how do i change it or if its anything else how do i fix,
    many thanks

  • Tristan Posted 16/10/2013 at 1:58 pm | Permalink | Reply

    i picked up the bulbs this morning from swell in hyde

  • Dan Posted 31/10/2013 at 6:36 am | Permalink | Reply


    My juwel lighting unit swtiches on for a couple of seconds and then turns off

    I have tried in a different socket and took the bulbs in and out and still doing the same

    Any ideas? Planning on replacing bulbs as over 12 months old


  • mike Posted 02/11/2013 at 7:56 am | Permalink | Reply

    Hello i have a trigon 190,my lights come on for about half an hour then go of again,if i switch them of and back on they come on right away but go of after about ten minuits,what could this be thanks mike

    • Simon Keegan Posted 04/11/2013 at 3:07 pm | Permalink

      Hi Mike you need to check your tubes. If the tubes are ok, if it’s in warranty contact whomever you purchased it from or contact Jewel customer support.

  • sean smith Posted 12/12/2013 at 8:38 pm | Permalink | Reply

    One of my units for my five foot tank has stopped working. I have lifted the unit from the tank and i can hear water swilling around inside the unit.
    How can i get the water out please? It is the light unit for the 5 foot bow fronted tank (i think it is the vision model)

  • sean smith Posted 17/12/2013 at 7:15 pm | Permalink | Reply

    I have a juwel vision 5ft tank and one of the light units has stopped working. Upon picking the unit up, water can be heard inside it swilling back and forth as the unit is tilted. Is there a way of draining the unit and get it working once again please?? The unit has never been under water and all i can think of is that the water has come from condensation or the airline splashing onto the unit and it has seeped in somehow. If you can email me at the email address i provided when sending this, it would be greatly appreciated. Many thanks and regards.

    • Jenni Hill Posted 18/12/2013 at 10:43 am | Permalink

      Hi Sean. We doubt that there will be a way of draining the unit and it sounds as though it is broken beyond repair if there is a large amount of water inside. It does sound like it could be splashing or condensation over a long period of time that has done the damage, since it has never been under water. Did you purchase the fish tank from us?

  • Crazy Sean Posted 20/12/2013 at 10:07 am | Permalink | Reply

    No i bought the tank second hand and it worked perfectly then. I was wondering if it was worth drilling a tiny hole inthe corner to act as a drain hole and seeing if it works once it is totally dry???

  • julie Posted 22/12/2013 at 5:21 pm | Permalink | Reply

    hi how do i replace the starter for the lights in my juwel trigon 350 thanks julie

  • Craig Posted 27/12/2013 at 5:42 pm | Permalink | Reply

    Hi I have trigon 350 and the smaller light unit just flickers on then off once when I plug it it then nothing . Changed the bulbs . Same thing
    Any ideas !?

  • Helen Posted 08/01/2014 at 11:07 am | Permalink | Reply

    Tristan did you solve this problem as ours is doing this we changed one bulb and in line rocker switch still comes on and goes straight off about to go get a second bulb to see if they both went at same time would be grateful to hear how yours turned out thanks

    • Jenni Hill Posted 31/01/2014 at 1:37 pm | Permalink

      Hi Helen. Sorry for the delay in getting back to you. Since you’ve already tried new bulbs it sounds like you may need a replacement. If you give us a call on 0161 351 4700 our aquatics advisor will be able to chat to you about this and may be able to send you a replacement if the item is still under warranty.

  • teenie Posted 08/01/2014 at 6:59 pm | Permalink | Reply

    both my lights go on in my jewel tank when switched on ,then few seconds later flicker off. this is an old unit. do you think i need a whole new light unit or replacing bulbs should be enough.

    • Jenni Hill Posted 31/01/2014 at 1:35 pm | Permalink

      Hi Teenie. Did you buy your light unit from us? If so, please give us a call on 0161 351 4700. Our aquatics advisor may be able to help you fix the problem over the phone, and if after trying a new bulb we find the unit is beyond repair, we might be able to replace it for you if it is still within the warranty.

  • Dorjee Posted 12/01/2014 at 11:32 am | Permalink | Reply

    Hi, my jewel Rio240, light unit start giving problem, when ever I put on light, it stay for couple of minutes, then start blinking, n after sometime it get off for sometime n get on for sometime, so it is very annoying, I changed new lamp,try out different ways. Atlast, I guess the transformer is the problem. But don’t know how to reach there, since it’s all sealed.
    Any help Well be highly appreciated.
    Even I like to buy secondhand light unit if someone got smashed aquarium of jewel rio 240…

    • Jenni Hill Posted 31/01/2014 at 1:32 pm | Permalink

      Hi Dorjee. Did you buy your light unit from us? If so, please give us a call on 0161 351 4700. Our aquatics advisor may be able to help you fix the problem over the phone, and if the unit is beyond repair, we might be able to replace it for you if it is still within the warranty.

  • sharon Posted 19/01/2014 at 10:52 am | Permalink | Reply

    Can I use a cheaper bulbs in a jewel fish tank or is it only the jewel bulbs that will work

    • Chris Walsh Posted 31/01/2014 at 1:25 pm | Permalink

      Hi Sharon.

      Yes, as long as the non-Juwel bulbs are of the same wattage and size it will work.

  • Steven Posted 25/01/2014 at 4:43 pm | Permalink | Reply

    Hello there a have a t8 light unit and the wire has snapped so how do a go about getting it repaired r replaced kind regards steven

    • Jenni Hill Posted 31/01/2014 at 1:29 pm | Permalink

      Hi Steven. Please give us a call on 0161 351 4700 and one of our advisors can look into this for you

  • jim Posted 28/02/2014 at 9:19 pm | Permalink | Reply

    my 180 t8 have gone and now my t5 are gone this isnt fair i love my tank and cant keep having to pay ouf for the whole unit again everyone i know has had this happen is there any other lighting i can use??

    • Jenni Hill Posted 10/03/2014 at 12:41 pm | Permalink

      Hi Jim. Did you buy this product from us? If so can you give us a call on 0161 351 4700? One of our advisors can look into this for you and see whether we can offer you a replacement

  • Nigel Emblem Posted 08/03/2014 at 12:51 pm | Permalink | Reply

    There is power to all four endcaps. New tubes fitted. Still not lighting?

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