Poorly Dwarf Gourami

Hi , I'm new to fish keeping, I've had my tank set up for 4 months now. I do weekly water changes and water tests. Currently my water tests have risen  a little ( ammonia 0.25 ), ( nitrites 0.25 ) & the biggest climber has been my nitrates, which has climbed from 40 ppm to 80 in a week. My tank is currently stocked with 6 harlequins , 6 neons which are all perfectly healthy. But 10 days ago I introduced a pair of dwarf gourami's. both of which settled in very happily. But I've noticed this morning that 1 of them, is hardly moving and is facing down, he only seems to move when other fish pass by. He also seems a little bloated. I'm not sure if its a swim bladder problem or maybe something else. Any thoughts please.

Thank you for your help sue
I have a 68 litre tank ,which I change 12 litres a week. The gourami's are 2 males, which I have been keeping an eye on, they don't seem to bother one another at all, as for the filter it's a hang on filter,which has 2 carb filters and 1 bio filter. The water is very clear, but have been considering an external cartridge filter, I would be grateful for any advice you give.

Many thanks

Dwarf gouramis can be nasty little things and I wouldn't be at all surprised if one wasn't picking on the other when you weren't watching. Given how weak they are that could be enough to push the one into being unable to cope. Unfortunately, knowing how iffy they can be, it wouldn't be a surprise if the one that's behaving oddly were to die. I'm sorry I can't be more helpful.

Personally, I don't like filters that have carbon catridges, but that's just me  Once you get the water sorted by doing large water changes for a few days, I would think about either replacing one of the cartridges with something like a sponge to give you more bacteria friendly media, or changing the filter if it is not powerful enough for the tank. If it came as part of a package with the tank, it could be underpowered as manufacturers seem to like giving you the smallest filter they can get away with.
If you do decide on a new filter, transfer all the media from your current filter, and fill in any gaps with new media. That way you keep all your bacteria. After a couple of months you can start to repace the old media, a bit at a time, with the new media that comes with the new filter.

Have you tried using the compatibilty checker on this site? Just go to the fish profiles, chose any fish you like and you'll find the way in under the fish details. Enter the tank details and the fish you have and see what it says about your fish and stocking level. I've just checked dwarf gouramis in it, and it does suggest having only 1 male.
If you do use it, enter your filter as an internal.




PS just seen your latest post - if the scales aren't sticking out, it could be reacting to the water conditions so a few biggish changes could help it. But it won't be helping having 2 males in there.
As a final check, can I suggest you google dwarf gourami iridovirus and check the symptoms. Some experts are of the opinion that all dwarf gouramis from fish farms in the far east have it by the time they are exported.