your a bit paranoid sargie, i post no differently with you, than anyone else. simply my style.
as for Juwel tanks i stand by my comments, Oh and their lights are known as a bit suspect too.
Plecos. i, honestly didn't need you to point out how big, some Plecos grow. of that i am fully aware. but as you point out, the BN, gets no more than 4 inches. so the validity of my knowledge is, in this case, proved. you, however, needed to look it up, and that's after you made a statement, claiming you had, enough, knowledge to, contradict what i said. as for the volume they need. that's where experience comes in. 15 g with larger filter area, not pump strength, seems to be an ok size for BN. though if you want a "community" tank, 30+g is a most. indeed a breeding couple can be kept in 20g. what the books say, and what, can, be done are often different.
i agree some fish need area to swim, some need it for territory and some need it coz they are filthy fish. only dirty fish need "pure" volume. the rest need area. a "common" pleco can reach 18-24 inches, it only needs volume for its waste and providing the tank is wider than the fish is long 4-5 foot long is big enough. but, lets say, a Bala shark needs area, not volume, as they are swimming machines. so 6-8 feet is a minimum, as they are shoaling fish, needing to be kept in 3's minimum, but the area needed goes up by very little.
ultimately you can keep fish how you like. and even keeping fish in "inappropriate" tanks does not mean you fish will die, though they will live shorter lives. you may not even notice your fish are stressed. its only when you graduate from someone who keeps fish, to a fishkeeper. that you begin to see what you can get away with and what you fish needs, are not always the same. as a fishkeeper, my job is to make an, unnatural, environment as healthy as possible. i don't always manage, but i try.
Oh dear, you are going to be upset, AGAIN. Juwel don't make "custom" tanks, not for customers anyway. and they make nothing in the uk. one of the main reasons the don't(make custom tanks), is nobody would buy them. there are many small firms that do custom tanks in the UK. all show much better Finnish and quality than any Juwel tank.all juwel tanks are made in Germany, or sourced from the far east. i guess there could be a small contractor in the UK, but not conected with tank building. as far as i know thy don't have an "official" office in the UK.