Ooooh and by the way after putting in the Agar and bringing it to a boil again you should let it cool a bit - 10 mins or so - and then ajust the pH level in the solution to 5,5-5,6 with citric acid.. (some species need higher)
I don't have a pH-meter so I'm think of buying some of those pH sticks you can get for the aquarium to measure - don't know if they're precise enough - but they will have to do..