yes, the foam should be strong enough to hold driftwood. I found the Great Stuff windows and doors expanded just slightly less than regular Great Stuff. It needs to expand around the edges to hold it in. You can carve away what you don't want later. Look at some of my photos and you can see all the heavy things I put in. I wouldn't worry about it taking up room. We are only talking about a few inches, and you have now given your hermies MORE ROOM to climb on things.

What I did was set the heavy things first, let them dry, then went in and foamed the rest of the area.

here is a good photo of how to set the heavy stuff.

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My name is Liz
Do what's best for the animal, not what's best for you.

Another thought. I
If you don't want to risk damaging your driftwood if the tank doesn't turn out the way you want it is to use the great stuff and put blobs of it where the ends of the wood will be. After it hardens you can simply carve out an area where the ends will sit. This will also allow you to completely remove the limbs to facilitate cleaning the enclosure.

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i cleaned the branches the other day, I simply got them wet and wiped them down with a paper towel.

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My name is Liz
Do what's best for the animal, not what's best for you.

yes that is very helpful! I think I get the faom part now. I can do that I think. So after I foam the heavy things on and then the between areas...what about sealing the tank..it is humid and I may put waterfalls in the water dishes eventually.

Plus, do I seal it then silicone the EE mix on top? This part seems the hardest to do and less forgiving. I woulnd't mind some seal showing through as rocks or something ya know..because I am not sure how I can possible cover the whole 55 (2-3 sides?) with silicone and EE. I understand it has to be small areas for the EE to stick..but isn't silicone thick and sticky...I I had Dave seal Sunshines tile down and that seemed alittle messy and difficult to get right.

DO I smear it or what? then smoosh the EE in...and go on to the next area?

What do you think will look best...just the back side or one or two of the sides done too. I think with the corner caddies I want to stick in the foam it will lok best with the sides done too. I just don't really want to see the faom..so maybe I can flip the (tapped background) I already have over to hide that?lol I am just hoping I can do this good =)

when I was applying the silicone, i used my fingers to smear it around. You need to coat the glass and let it dry since the GS (great stuff) won't stick to glass. Once the GS is cured, about 48hours, you can then carve it with a utility or kitchen knife if it got bigger than you wanted it to. Then, i once again use my fingers to spread the silicone over the GS. I do it in little bits. Silicone about 12 square inches, then sprinkle EE over and pat down. I used one hand for spreading, and one hand for sprinkling. Plan on 3 tubes of silicone and 2 cans of GS. Get a bunch of latex gloves. For getting the silicone out of the tubes in larger quantities, i cut them open with a utility knife and scooped it out with a spoon.

So here you go.
1. smear all the glass you want to cover with Silicone II. I used black. Wait till fully dry.
2. Soak Eco-Earth brick in water to expand brick. Place in baking dishes in the oven to dry out. Must be 100% dry or it won't stick.
3. Attach branches, wood, bark and anything else to Silicone by setting in Great Stuff. Let Great Stuff cure for 48 hours. You will have to do one side of the tank at a time. Let gravity work for you.
4. Cover remaining areas with Great Stuff. Let cure 48 hours.
5. Carve out any unwanted Great Stuff.
6. Smear Great Stuff with black or brown silicone II, 12 square inches at a time or less. Sprinkle with eco-earth and pat down into wet silicone. Let dry.

This is time consuming. You should plan on 2 cans of GS and 3-4 cans of silicone. You will need ventilation, the silicone is smelly.

__________________
My name is Liz
Do what's best for the animal, not what's best for you.

ok I didn't know the GS did't stick to glass good to know. Also then maybe I should wait till spring for this since I need ventilation..don't want to kill my birds in the basement ya know.

How much EE bricks do you think it will take? I have three already done mixed with alittle sand and I have alittle Coco bedding (half bag) left. I think I may just use the EE mostly though cause cocobedding is expensive.

Then I will work on the waterfall pools first so I know where to cut the GS to fit the pump and pools. I am not sure how I am going to do that yet also...so I guess maybe I should figure that out first to plan how Iam going to do the walls and driftwood and levels.

Thanks so much for all yor help everybody. I may be back when I have more questions when I get started.

I would be careful with using any type of silicone on expanded foam. Though I know many have used it with success. I've tried it once and the silicone lifted away after a short time. I would recommend epoxy hard or a polyester hard thats food grade, they really stick to anything and dry to a smooth easy to clean surface if you should decide not to flock it with hummus or something else. It can be costly but can be found online in larger amounts for a good price.

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my 90 gallon took only one brick of coco-husk.

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My name is Liz
Do what's best for the animal, not what's best for you.

is epoxy water resistant? what color is it? I was thinking of just putting EE onparts of the wall and not on others so it looks like rocks and cliffs. Plus, I wanted to put some tile adhesive or something like that over the plastic caddies I have in the tank as levels...

what about Epoxide resin? I read that on the link from Venus for humid or water tanks. what color is that...do I have to add the EE over that?

what if I use the water resitant Epoxide resin (don't know what it is) and then use what ever silicone is left from the step one to add some EE and moss on parts of the wall...and then just keep the rest "rock" like. That would look good in my head ha ha!

I like that epoxy is easy to wipe down/clean. umm, if that looks like rock or if there is a way I can add a rock color (black or gray) to it then that would be less silicone and EE I would need to mess with.

However, I may need to add some tile adhesive (is that safe for pets?) for texture the crabs could climb that...but I am not sure how that is resistant to humidity? I would only need that on the rock like parts of the wall.

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My name is Liz
Do what's best for the animal, not what's best for you.