I've been researching epoxy clays and their formulations since the beginning of the year.
The main issue you run into, is something called "nonylphenol" and "alkylphenol". These are used as both an epoxy filler AND more specifically for nonylphenol as a catalyst to rapidly set the epoxy. The problem is that the nonylphenol is not used up in the reaction as it is a true catalyst. This in turn resides in the epoxy matrix and can leach out into the water over time. Nonylphenol was banned in UK a few years ago due to its massive overuse in many various industries and extensive damage to aquatic life as it very toxic to aquatic organisms.
Here in the US, however we still continue to use and produce it by the tons (literally) every year. It is used in epoxies listed as "safe for potable water contact" here in the US but banned from almost all use in UK. The main issue you are going to find, using any of the epoxy clay products sold here in the US, is that ALL I have found use nonylphenol and/or alkylphenol in its curing agent. Even the ones who don't list it on their MSDS, when you email the company they do agree that it is in there. ( A side note about MSDS, they are not regulated or looked at until an OSHA violation/lawsuit comes up. Companies can claim what they want and hide what they want. Don't just go by the MSDS.)
Epoxy putty is a great material. But I don't use it for my aquarium backgrounds due to the unavailability of a nonylphenol free epoxy putty. If your design is used outside of 100% submersion with fish, you should be ok, but I wouldn't use it in large amounts underwater. Not until there is an established safe material designed exclusively for this purpose.
The main issue you run into, is something called "nonylphenol" and "alkylphenol". These are used as both an epoxy filler AND more specifically for nonylphenol as a catalyst to rapidly set the epoxy. The problem is that the nonylphenol is not used up in the reaction as it is a true catalyst. This in turn resides in the epoxy matrix and can leach out into the water over time. Nonylphenol was banned in UK a few years ago due to its massive overuse in many various industries and extensive damage to aquatic life as it very toxic to aquatic organisms.
Here in the US, however we still continue to use and produce it by the tons (literally) every year. It is used in epoxies listed as "safe for potable water contact" here in the US but banned from almost all use in UK. The main issue you are going to find, using any of the epoxy clay products sold here in the US, is that ALL I have found use nonylphenol and/or alkylphenol in its curing agent. Even the ones who don't list it on their MSDS, when you email the company they do agree that it is in there. ( A side note about MSDS, they are not regulated or looked at until an OSHA violation/lawsuit comes up. Companies can claim what they want and hide what they want. Don't just go by the MSDS.)
Epoxy putty is a great material. But I don't use it for my aquarium backgrounds due to the unavailability of a nonylphenol free epoxy putty. If your design is used outside of 100% submersion with fish, you should be ok, but I wouldn't use it in large amounts underwater. Not until there is an established safe material designed exclusively for this purpose.
