Glutaraldehyde - The Highest Purity
0-18ºC 16220 Box 10x10ml ampoules 21.00
You can do a 1:9 dilution (10 mL glutaraldehyde to 90 mL of water) to give you 100 mL of 2.5% solution per ampule. That's 1 liter of glutaraldehyde for $21 + shipping. Although some other places might sell bulk for less (not sure, haven't checked) this type of packaged glutaraldehyde is preferable since each ampule is packed in inert nitrogen so there's no breakdown or adverse reactions since it's not exposed to air/oxygen. You can mix up 100 mL batches and dose them as needed so you won't waste much of it.
Heck, if you have larger tanks...
0-18ºC 16521 50% Solution 4x1 liter 67.00
1 liter solution to 19 liters of water will give 20 liters of a 2.5% solution. This is 4x1liters of glutaraldehyde, so you'll get 80 liters. For $67 + shipping. Less than a buck per gallon!
I'm not sure why the riccia is dying. Are you dosing straight into the tank? I suspect that if the entire bunch of riccia is being hit with too concentrated a solution of glutaraldehyde, the fine plantlets won't be able to recover & will die slowly. Try to add the glutaraldehyde in a very diluted form.
Allen, you said the riccia died slower in the 60 gallon tank. I think it's because as you added the glutaraldehyde, it was more easily diluted in the 60 gallons before it hit the riccia as opposed to the 10 gallon tank.
Maybe when you do a WC next time, add the dosage into a bucket of water instead of dosing straight into the tank. Or you can try adding a bit at a time, throughout the entire length of the tank and avoiding the patches of riccia?
I'm looking forward to the remainder if your experiments!