Bigger Powerhead??

You'll find the subject of Juwel filters is one of controversy. Some people love them, others hate them.

Generally speaking, you need a turnover of 5 times the tank volume per hour. But I'm sure I read somewhere that Juwel's idea is that a slower water flow means the water, with its ammonia and nitrite, is in contact with the media for that little bit longer on its way through the filter. The built in filter is OK if you don't stock the tank to the max, and if you avoid messy fish. Algae eating fish (eg plecs) and some big cichlids are the prime examples of messy fish, though you won't be able to have the likes of an oscar with 180 litres.
I have a Rio 125 and I removed the built in filter, but my main reason was the noise. I've never heard of anyone else with this problem, I even tried a new powerhead to no avail.
Yes, you could try a more powerful powerhead, just make sure it'll fit. Or you could get another filter - an external would be best for a 180. As you are not far into your cycle, you would only be losing a few days if you chose to get another filter. Or even get another internal to run with the built in filter, though that would take up more room in the tank.

If you decide to keep the built in filter, even with a bigger powerhead, just a word about the media. In mine (I've had it a few years) there were coarse and fine blue sponges, a green sponge, a black sponge and a whilte pad. You'll most likely also have a box of cirax which was brought in after I got my tank. Ignore everything the manual says about changing the media 
Cirax needs to be changed in a few years' time when it starts to crumble; the blue sponges need to be changed in several years' time when they start to fall apart. Until then, squeeze the sponges gently and swoosh the cirax box in old tank water that you take out during a water change. You only need to remove the debris off the sponges, so don't overdo it; they'll never look like new again.
The green sponge (if you have one) isn't very good at removing nitrate like they say. But it is a good home for the filter bacteria, treat it like a blue one and don't change it.
The black sponge has carbon in it. You don't actually need carbon. It will grow bacteria in it, but carbon gets used up very quickly so this is one sponge that is supposed to be changed frequently - and the cost will build up. At this stage in a cycle, there won't be many bacteria in it. I would take it out and replace it with another blue sponge - or leave the space empty in case you ever do need carbon. Its main uses are removing the brown colour that leaches out of bogwood and removing medication after treatment has finished.
The white pad - this will need changing frequently. Unlike most filters, Juwel puts the white pad at the start of the water flow to stop debris getting into the sponges. It will clog quickly and won't go back to shape after washing. I only managed one wash per pad while I was using the built in filter. Buy a roll of filter wool (pond stuff is cheapest) and cut it to shape.

Hi Mervyn

I too run a Juwel Rio 180 and toyed with the idea of removing the internal filter and running an external. In the end, I decided to run the two of them together. The internal is quite fixed to the glass and with a full tank,  I decided it wasn't worth the hassle. Just something for you to perhaps consider...?

I removed the filter from a Rio 125, and I did it with fish in the tank 

The secret is to do it in the middle of a water change so the water level is lower. The black box is held in place by 8 blobs of silicone. You need a long flexible blade (I sacrificed an old kitchen knife) and be very careful not to touch the corner sealant or the tank will leak. Pull the top of the filter gently away from the glass and saw through the 2 upper blobs on one side followed by the upper ones on the other. Then you'll be able to pull the box further out to do the lower four. I used a stanley knife blade - carefully - held almost flat against the glass to scrape of the last of the silicone. The reason the water level should be lower is that all the sawing creates a tidal wave.
The heater is inside the box so you'll need to find another way of attaching it to the tank wall. It used to be possible to get heater holders, black cylinders with suckers. But having broken the one for my quarantine tank heater, I couldn't find anyone selling them. So I got suckers with a ring attached. Two of those hold a heater nicely.


As for upgrading to an external filter, it's quite easy. If you have cirax, empty the box in with the ceramic media that comes with the external - they normally contain ceramic noddles or balls for one layer. With the sponges, either put them where the external's sponges go, then chop up the new sponges to fill in the gaps, or if there are several layers of ceramic media, bury the sponges inside the ceramics. So long as you get all the Juwel filter media inside the new filter, even if you have to cut sponges to make them fit, you shouldn't lose any bacteria. Make sure the old media is kept wet all the time, and monitor your ammonia and nitrite levels for several days after, doing water changes if either of them show above zero.
Feed the fish lightly for a week or so to reduce the ammonia they make, and don't get any more fish for a few weeks after changing filters to make sure the new filter has settled in.
Leaving the media inside the tank won't cycle new media or keep the bacteria inside old media alive - the bacteria very much prefer to grow in places with a high water flow bringing their food and oxygen. This is why most of them grow inside the filter - a place with a high water flow. But running two filters together for at least six weeks will help, though you'll end up with the bacteria spread between the two filters so when you remove the old filter you will lose some.



To give you an idea:
I upgraded from a 60 litre tank to the 125. The filter in the 60 litre had a long thin rectangular sponge and a box of ceramic noodles. I put the ceramic noodles in a net bag and cut up the sponge till it fit in the Juwel filter box. I used the 2 blue sponges that came with the tank and replaced the black and green sponges with the old media. I never saw even a blip of ammonia or nitrite.
Then a month later I took out the Juwel filter and replaced it with an Eheim aquaball internal filter. This uses hollow cylindrical sponges and has a small box for ceramic media. I crushed the noodles to make them fit in the box, then chopped up the sponges to make them fit in the cylindrical baskets. I made sure I used the sponge from the 60 litre tank first as that would have still had more bacteria than the newer Juwel sponges. Again, I never saw any ammonia or nitrite. I waited a few months then took several months to replace the old media with proper eheim media, one basket at a time.