Acrylic & Greatstuff

I have used the great stuff/silicone method on both glass and acrylic tanks with no problems. You don't need to sand the acrylic to get the silicone to stick. I didn't notice the silicone taking a long time to dry, but I was only working on it on the weekends, so it had a full week to dry before I came back to it. I actually embedded coco husk chips in the silicone over the Great Stuff rather than peat or coir dust. Everything has held up to daily misting for the past 9 months.

You can get the same effect without using the low expanding type just by slowly buiding up the base and not adding too much at once. Wait 24 hours (for full expansion of your base layer), and add your buildup layer.

Yeah, Rich, my acrylic tank was made by the same guy that made yours. I had to make some silicone seals, too. Mine work fine without sanding. The trick is to make sure you have a perfectly clean surface--no dirt, no moisture, etc. I used rubbing alcohol to clean and dry. No leaks.

hicksonj said:

Since acylic is at least a partial petroleum byproduct, maybe this causes the sealing difficulties.

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Joe, that is exactly the problem with acrylic. Not all the oily hydrocarbons get cross-linked, and some remain as a residue on the surface. It doesn't matter how "new" the acrylic is--newer acrylic will actually be worse.

Sanding will help because it leaves undercuts for the silicone to adhere to, but you will have a scratchy haze wherever you do this. I don't know if I would use acetone on acrylic, as my guess is that it would cause a haze by denaturing some of the acrylic since acetone is a pretty strong organic solvent. Anyway, after cleaning and using alcohol, my background, my seals, and the seal around my door have all stood up just fine--and the seal around my door takes quite a bit of abuse.

Since I've had mine set up longer than Rich has had his, I would think that any structural failures would be apparent by now. Regardless, there is usually more than one way to skin a cat. You don't need to be belligerent just because I don't use your way, Rich.