As there should be also some German here, maybe somebody can help me with the translation of “Fishpaper”.
In AliExpress I found something the same under the name “Gerste papier”.
Unfortunately the AliExpress translations a bit…so so… 
And I couldn´t find something with the name “Gerste papier” on german sites.
So if somebody knows any similar product to the Fishpaper everyone talks about when it comes to building a proper battery, I would be very glad to hear it!
Elektroisolierpapier
Total blöd … Unter “Fisch Papier” wirst du nichts finden. XD
Wow thanks! Just found a lot of cheap fish paper on AliExpress by searching “barley paper”. It looks like it the same everyone has. Im going to buy it. Here’s The one I’m going to buy
the same I found. looks the same everybody use. but not 100% sure.
looks like the material the extra covers for the +pole also made of.
I read once this covers add up the isolation, but burn like hell…
does somebody know how about the fishpaper (or elektroisolierpaier),
it´s fire prove or as min. fire resistant for a time? 
besorg dir einfach bastelpappe, ist nix anderes. edit: ok richtiges isolierpapier ist wohl was anderes, aber ka, sieht nach overkill aus.
Proper fishpaper is mostly made out of mineralic fibers that are non flameable. The finished paper may deliver some kind of potential flameable energy to your batteries but only a very low one, I would guess it is in fact non flamable and only carbonizing when the battery burns down.
Buy some and try to ignite it with a flame torch to solidfy that guess.
Fishpaper is king! I also use it as underlay for pre tinning of flat copper wires and for any solder joints at battery. Fishpaper has no problem with 500°C where my silicone mat melted. It gets a bit sticky but no damage at all.
From my experience and tests everything burns when you use a torch or fire, silicone, neoprene,… More important for me is that the materials are enough heat resistant. If a battery is burning then it makes no difference if the neoprene foam or fishpaper is burning, too 
that´s my intention behind. If it burns it burns, but a spark shouldn´t cause a fire. how to identify real fishpaper on plattforms like AliExpress? Just buy, hope it´s the right and then look what I got? or there some more details about which material thickness etc. which can help me to find it?
Haha, hatte ich auch schon gesucht. 
When it comes to preventing shorts theres no such thing as overkill.
500°C, i think the short is the least of your problems^^ But yes, preventing short is king.
Anyone knows a EU source for this magic fish paper?
https://www.akkuteile.de/abstandshaeuelle-faeuer-18650-zellen/a-400301/ if you want to go full protection^^