Polyurethane near an established tank

[Sleepydoc]

The finish on the front lip of my stand, down by the sump has started to degrade and I need to add a couple of coats of polyurethane to it. Does anyone know if using polyurethane near an established tank will cause issues? I know water-based poly uses ammonia as one of the solvents, so I’m going to use oil-based, but I cant find anyone who’s used it near an established system

 

[Ocelaris]

Worst case use some carbon in the tank. I doubt the fumes will cause an issue. I personally use target coatings for my finishing, and it's very low voc. I'd highly recommend them over home depot based poly.

 

[Sleepydoc]

So just to update, I went ahead and did it. I ended up using cheap, Minwax oil based polyurethane from Lowes and it went just fine. 2 weeks later all my inhabitants are doing well with no sign of stress either at the time or now.

I don't know if my thought process was correct, but it went something like this:
All polyurethane varnish has some sort of volatile solvent that evaporates off, leaving the polyurethane behind along with fumes from the evaporated solvent. For traditional, oil-based polyurethane, it's a some sort of hydrocarbon. For water-based, it's generally a glycol ester, although I've used some that at least smell like they have a component of ammonia in them as well.

For water-based coatings, the solvent is by definition water soluble, where as for oil-based coatings it is water insoluble. As such, the fumes created by a water based coating would be much more likely to get absorbed into the tank water and potentially cause issues, where as the opposite would be true with fumes from the oil-based solvent. Of course that assumes equal toxicity at equal concentrations, etc, so it could be totally wrong, but it sounded good in my head, and in the end things went fine.

Thanks for your help!

 

[Fam5dad]

This is a topic of interest to me because we are going to have our floors refinished. I am just finishing my cycle and to be safe I don't want to add much more than fish till the floors are done, but that is months from now when we are gone on vacation. The wait will kill me! LOL. The contractor says he will use an oil based polyurethane which goes along with our water insolubility thoughts. Ill put a big bag of carbon in that week too. Anyone have their floors finished with a reef tank in the house?

 

[Ocelaris]

Water based is what commercial applications use these days. I'd recommend that strictly from a durability perspective. Water based and oil based can come in both 2-part (cross linker) or a old school evaporated finish which is what you don't probably want as it's less durable and gives off more fumes. I've used water based 2 part for both of my last two houses and they were very low odor (voc). It's an old thread, and there's lots of good details here.