I have killed way too many fish with my own fuzzy headedness, If they are alive now when you do a waterchange it should be all right. I would definately do a big one though! haha. Maybe it will be a fortuitus error.
BettaTalk recommends using 1 tsp of salt per 2.5 usg always in Betta water (along with 1 drop per usg of Aquari-Sol) all the time. So that equals a Tblsp--Right? So the Betta should be ok!
As I said above, some things I just have to try and go by my own experience, because ther is just no agreement in the hobby. If we can agree to disagree I think we are doing well. B)
DISEASE: FUNGAL INFECTION
uGENERAL INFO:
If you always add aquarium salt to your betta’s water (1 teaspoon of aquarium salt per 2 1/2 Gal of water) and one drop of Aquarisol per gal, your betta will probably never get fungus. It is contagious, but bettas will more than likely recover if treated promptly.
uSYMPTOMS:
Betta has white cottony like patches on its body or head. He may be less active, may have stopped eating, fins may be clumped, color may be pale.
uTREATMENT:
Do a full jar water change. Add “Fungus Eliminator†by Jungle (included in our Betta First Aid Kit). These are crystals are dosage should be about 30-40 grains per 1/2 gal. Water should have a nice gold color, not too dark. Do not overmedicate! Change water every third day and add a new dose of same medication. Continue until all fungus has disappeared. Then keep betta jarred for another 2 weeks at least and instead of Fungus Eliminator, just add 1 drop of BettaZing in your betta’s water to clean any other bacteria/fungus that may still be present.
(this is copied from BettaTalk)