Re: not sure on filters
#8
190L isn't big enough for weather loaches. I have three in a rectangular 240L, and that's the smallest tank I'd give them, and even then I think its a little too small. They do better in groups (at least 3+) and need a fair bit of floor space (4'to 5' x 2' really). A Trigon 190 isn't big enough. They're also pretty messy, so I'd recommend an external if you wanted to keep them. TBH goldies really need an external too.
They don't mix well with the fancier fancy goldfish, as they're pretty boisterous, but they'd probably be ok with fantails. I wouldn't put them anywhere near Celestials for example.
Personally, I don't like goldfish, and would encourage you to look at other "coldwater" fish. In a 190L I would look at some of the more interesting coldwater fish. A large shoal of 20+ White Cloud Mountain Minnows would look great. Setting up a river tank is difficult in a corner tank, as you can't easily set up powerheads and filters to give you unidirectional flow. That rules out many of the temperate bottom-dwellers, such as Gobies and Hillstream loaches, but if you planted densely then you could have a group of American Flag Fish (A killifish that thinks its a cichlid). Odessa Barbs would also be a good choice. Many of these fish (apart from the loaches) prefer harder, alkaline water, so would be fine in your tank.
The only problem with temperates is sourcing them. Very few places stock them.
Loaches, Barbs, Minnows & Shrimp! Oh My!