False Positive On API Ammonia Test?

I have heard of Biohome Ultimate media which is supposed to grow nitrate eating bacteria like bioNitratEx, though it also takes a while for these bacteria to colonise.

I use this. I had a Nitrate problem in my very well-stocked tank and high Nitrate tap water and, some months later, the Nitrates in my tank are less than the 50:50 tap water:RO water I use at water change time.

I looked up Biohome Ultimate and it looks really promising, and it's inexpensive, thank you for the suggestion. How much of the media would I need for the Bioflow 3 filter (for Juwel Rio 180) and how to put it in? Some sort of basket like one for cirax would be good or a mesh bag perhaps?

If you order the Biohome Ultimate you get sent a decent sized bag of it - 500g. I've put mine in a couple of mesh bags, but I don't know the set-up of your filter.

You might want to consider putting some of the BioHome in one of these. An air driven filter. I'd use one in a Betta tank..... and probably set up one or two as additional filtration in a bigger tank - especially one with an internal filter. You can see the size of the bag of media you get in this video.

Plenty of room to stack loads of biohome in there  . Change your sponges so the water flows through the coarse sponge first, then the fine, and then the biohome media. You'll have to do some juggling 'cos you'll want to keep as much bacteria as possible, so you might have to change some media over each month or so. Any fancy sponges that are carbon impregnated or whatever can be put in the cupboard. Sorted!!

Thank you Colin and Sue, Biohome media and mesh bags are on their way! 

I'll make sure I won't fish out all of the bacteria in one go, I might slice sponges in order to remove them bit by bit. But I wonder if I should put the Biohome last, after the two blue fine sponges as Colin suggested. The guy who sells the media also seems to recommend that:
 
"Ensure that there is a good level of mechanical filtration before the media to prevent clogging.
The media is used in the final chamber of a filter to provide biological cleaning of the water. The foams / vortex / screens before the media chamber will act as a mechanical filter and remove suspended solids from the water."

With a Juwel filter, the white pad and coarse blue sponges are the mechanical media, and the coarse sponges are also biological media. Cirax is purely biological, and the fine blue sponges are biological and get the fine bits that go through the coarse sponge. I notice the Juwel recommend putting cirax before the fine sponges, so maybe between the cirax and fine sponges. I never had cirax, that was introduced after I got my tank.