> the "tanks" here are university lab near industrial scale plastic 10,000l tanks
Likely polymethyl methacrylate (PMMA), usually called acrylic, and possibly but less likely polyethylene terephthalate (PETE). Both are technically plastic, but plastic often correlates to cheap, and I doubt those tanks are cheap. Also possible but even less likely to be aluminium oxynitride (ALON), which is ceramic not platic, aka transparent aluminum, but I suspect it would be cost-prohibitive.
> ...they know what their doing... I welcome corrections
Likely polymethyl methacrylate (PMMA), usually called acrylic, and possibly but less likely polyethylene terephthalate (PETE). Both are technically plastic, but plastic often correlates to cheap, and I doubt those tanks are cheap. Also possible but even less likely to be aluminium oxynitride (ALON), which is ceramic not platic, aka transparent aluminum, but I suspect it would be cost-prohibitive.
> ...they know what their doing... I welcome corrections
--> they're ;-)