Can I rse Aldon sealers on my fishpond or birdbath?

No. Even though we might think that by waiting sufficient time after sealing there should be no harm to fish, DO NOT RISK IT. Find something from another manufacturer that specifically says that fish ponds or bird baths are an approved application.

Can I use Aldon sealers to waterproof my (fountain, pond, waterfall) or other water holding structure.

It depends on the situation. Aldon sealers are not specifically designed for that application, but there is no reason to think they would not be beneficial. If the containment area is very porous and there is many feet of water depth, you might need to find something that is rated for that purpose. We know that people have used the sealers for small fountains and waterfalls with success, but do not have enough history to make that recommendation more strongly.

Note:
Sometimes, despite your diligent research and the best of intentions of your suppliers salesperson, you might have been given the wrong information. Therefore, no matter how confident you are, whether first time user or seasoned professional, it just makes good sense to patch test a small area and evaluate the results in a few hours before doing a large area.

Most Aldon sealers have more than one area they can be used in any project. Check sealer information on the web site.