use a smaller razor loh lolz..
but since u fill up half volume i think its fine.

one easy way to check is by filling up to 80-90%,
take a look from the top and see whether it got curve up in the middle of the tank or not?
or use measuring tape to check left right and middle to see whether they are of the same length or not.

its very dangerous esp genie's tank which is juz 5mm. if got ppl in front when it breaks 

Yes it is.

so normally i will just use standard tanks and fill up half the water,
but there is another problem as the dry portion of the tank will become blur overtime 

tat doesnt help much actually, have u ever seen those car light ?
after sometime u can see there is a layer of blur stuff on the cover.
its something like tat and scrubbing can reduce it but cant completely remove it.

how you cut the tank into half?

Suitable for newt. Anyone know where can get living moss ?

terrestrial moss, as for aquatic, i'm using java. But dries up pretty quick.

Erm, it's a business I run, I own a gallery n sell stuffs there? I don't know how to explain by just typing in words. May be I come up with a blog in near future to share my experience of starting this whole business thing? =) Anyway, I welcome you to visit my gallery too!