Mods may want to move this into a new thread within the same forum!
Not a Dane myself (Italian), but living in DK since quite some years.
Obviously evaporation may alter your salinity, but it should be really in large amounts to make a difference. Otherwise, no, I stopped checking salinity long ago. Also, the hydrometer is a very unprecise instrument, heavily affected by temperature. I prepare the salt water at the SG (@ 25 C) I want before adding it to the tank (I check temperature by finger (!), and use my shower to fill buckets where salt has been previously distributed). Really, no need to be particularly precise, as long as you deal with these small SG numbers, and allow only small variations. For example, nowadays I fill in salty water only every 2-3 water changes, giving the plants a break and allowing some salinity fluctuations, which is good for the fish.
Great bunch of fish you have in there! So, you have a beach for the skippers? That's was my very first plan!! I've been discouraged by a number of factors, among others a long
conversation with Neale Monks. Also, are you sure of the species? The Atlantic (
P. barbarus) tends to be a real bastard, at least with its conspecific.
Me, with three nasty archers, I can't keep much else in there. Considering a nice
Procambarus clarkii, which they'll probably leave alone, given its size, but it will reduce the plants to a pulp. So, since I decided that this is my last attempt with plants, if I don't succeed with them I'll get one!
I'm a mangrove nerd, but I haven't still seen mudskippers in all my travels!
Cheers!
Maurizio