Here's the best advice
I've seen regarding disinfecting plants. I copied it from the Aquaria: Plants FAQ, by multiple authors, in January of 2000, and it still is good advice:
``How do I disinfect my plants?''
New plants may have unwanted hitchers: snails, algae or disease.
Disinfection can help reduce their transmission into the tank, and can
be used to remove algae growths from established plants. Beware, there
is always a danger of going too far and damaging the plant itself.
Some popular methods:
* A ten minute soak in potassium permangenate (pale purple) works
well; it is available in dilute form from Jungle products as
"Clear Water". Permangenate is particularly good for killing
bacteria and pathogens.
* A 2-day soak in 1 tbsp/gallon of alum (buy it at drug stores) is
good for killing snails and their eggs.
* If the plants are kept in a fish-free system for three weeks,
parasites like ich and velvet will die without their fish hosts.
* A soak in a 1:19 diluted bleach solution; 2 minutes for stem
plants, 3 minutes for tougher plants. Make sure to remove all
traces of bleach afterwards by rinsing with water and
dechlorinator. This method can kill your plants, so use only as a
last resort against hell algae.
(See the ALGAE SECTION of the DISEASE FAQ for more algae-prevention
tips, and the SNAIL SECTION of that same FAQ for snail prophylaxis.)
``Do I leave my new plants in the pot?''
Many aquatic plants are now sold in potted rockwool. Plants with
delicate roots, such as Cryptocoryne and Anubias, are usually best
left in the rockwool wadding, especially if you have to move them
around in the tank. Leaving them potted also can reduce transplant
shock; otherwise you must be patient and allow the plants time to
recover in their new substrate. You can bury the pots in your gravel
to conceal them. Some folks like to cut away the plastic pot, and just
leave the plant in the wadding so it can grow out into the substrate.
Snail Prophylactics
To guard against unwanted snails, use a weak potassium permanganate
solution. The Manual of Fish Health recommends a concentration of 10
mg/l as a 10-minute bath as a general disenfectant for aquarium
plants. Then rinse them in running water. This kills snail eggs and
parasites and might guard against algae spores.
Alum is also useful. Get "Alum U.S.P." at the drug store. Soak the
plants in a gallon of water that has up to 10 teaspoons of Alum. The
Alum kills microscopic bugs. Longer soaks (2-3 days) will kill snail
eggs and/or snails.
Now, back to me. I find that you have to completely submerge the plant in order to do the job right, so I use a 6 gallon bucket and this device that I fashioned out of the eggcate flourescent light lens material available at all the home improvement stores.
