Are you okay with this being strictly better than Island? Wizards probably wouldn't be, but I see you've got another cycle (The Arcanum and friends) that are also better than basic lands, so it may be that you're just disagreeing with that design principle.

I figured that the drawback of none of your Islands (itself included) untapping for a turn would balance it. That and the fact that its second ability only produces colourless mana. Have adjusted it to 'Lands you control don't untap' to make the drawback mean a bit more.

Sadly it doesn't matter how bad you make the second ability; as long as it can tap for without drawback, and has the option of doing anything else, it's still better than an Island. You could separate the drawback onto its own line so that it applies to the tap-for- as well: "Whenever ~ becomes tapped, it doesn't untap during your next untap stap". That'd make it no longer strictly better than an Island.

Separated it & reverted it to Islands not untapping.

That's a much better design. This is now an interesting choice whether to play it over an Island; many blue decks wouldn't, but some big-mana decks or artifact decks might well do. I don't know whether it might be pushing Cloudpost's territory, but I think this works well now.

which is what it was always designed for.

You've edited this back to being strictly better than Island.

oops left a few vital words out. Was changing it to when this is tapped for mana triggering Islands not untapping. The old wording your opponent could tap this wityh say an Icy Manipulator and cause all your Islands to tap.

Ah, fair enough. Technically, you now need a linebreak before "Whenever ~ is tapped for mana...", since it's a separate ability.

Cool card.

Thanks, has been through the wringer in development but I'm happy with this version. Everyone has been reasl==l helpful.

Nice. Powerful but not too powerful, very very nice if your deck is playing blue but not mono-blue, so you get a big boost but don't leave your opponent open for a turn. It honestly may still be too powerful, but it could easily be ironed out in development/testing by adding some amount of to the activation of the big mana ability.