Thoughts

[tank o tang]

I like the look of a wall against the back glass but don't like the foam a epoxy part. I was thinking of drilling 2 small holes through a piece of rock then stringing them up on the eggcrate with fishing line (don't want to see zipties). Instead of using the foam I was going to trim the eggcrate so none was visible in gaps (leaving back of tank to show through). Think it will work without foam or will it look funny?) Was also thinking I should brush some crazy glue on the eggcrate and spread sand to get rid of white color.

 

[fishieness]

I think it would depend on the pieces of rock and the structure you use. As if you trim enough or the pieces are large but thin, you won't get much support and it at least has a chance of falling over.
I also think the zip ties would look funny, so you would have to find specific pieces that have a thin back (perhaps part of a branch) and then widen out to hid the zip tie.

 

[mikelaubach]

I am doing a combination of the two. I have crated a large structure that has a hole in the bottom center towards the right of center. This is to look like a cave, and the tank wall (painted black) will show through. I put rocks along the edge of this opening as ledges to further produce the cave look.

The foam adds a substantial amount of structural integrity to the plastic eggcrate. I do not think I'd do just eggcrate and rock. I have about 25 pounds of rock on mine (65G tank) including an arch (flying buttress is what it really is) and even without the eggcrate trimmed, it was incredibly flexy. I used zip ties and mostly buried them in the foam, as I too did not want to see them, but wanted as tight of a structure as I could get.

Once the foam is on, you can cover it with epoxy and sand or crushed coral to make it look more natural. I even bought salt for water softeners and sprinkled that over the foam after spraying it and allowed the foam to harden with the salt there. Now I need to wash the salt off, and it should leave the foam with more jagged edges, which will look even more realistic once covered in epoxy and crushed coral. I'm using the Bob Smith Industries 20-minute finish resin from a model store in Wallingford.

I have to start a build thread for mine, but everyone wants pix, so I've been collecting pix as I go and will load up the pix when I start the thread. Just wanted to give you an idea of the massive flex in the structure as you are proposing, and a way to make the foam disappear immediately instead of having to wait a year for the foam to be completely covered in coralline before it blends in and "disappears."

 

[tank o tang]

Thanks, looking forward to the thread. To stop it from falling over I was going to try a find/make some kind of plastic clip to attach it over the back trim (maybe a shower curtain ring). Only thing I could think to compare it to are the clips to hold a screen top on a hamster tank. This should stop it from falling forward. For stiffining it up what do you think about taking a piece of acrylic and cut a large, skinny triangular pattern to give it some strength (would have to attach this first then make sure I fishline the rocks along these supports to hide).

 

[mikelaubach]

It's a possiblility. Some 1/4" plexi should help strengthen it up quite a bit if that is the route you decide. Might help to tie the rock and various points of the eggcrate as well. I've not tried it, but give it a whirl.

 

[erbgo]

plexi would stop water flow between rocks would make dead areas jmo

 

[fishieness]

i believe mike was saying to attach the plexi to the back of the eggcrate against the wall for structural support, not in between the rocks.

 

[Kdocimo90]

<a href=showthread.php?s=&postid=14206416#post14206416 target=_blank>Originally posted</a> by fishieness
I think it would depend on the pieces of rock and the structure you use. As if you trim enough or the pieces are large but thin, you won't get much support and it at least has a chance of falling over.
I also think the zip ties would look funny, so you would have to find specific pieces that have a thin back (perhaps part of a branch) and then widen out to hid the zip tie.

+1!

 

[mikelaubach]

<a href=showthread.php?s=&postid=14209096#post14209096 target=_blank>Originally posted</a> by fishieness
i believe mike was saying to attach the plexi to the back of the eggcrate against the wall for structural support, not in between the rocks.

Exactly. Create what one normally would using the rocks and eggcrate, and then attach the plexi to the back of that as a large (or largish) single piece. I don't know how it will look, nor how stable it will be, but it's the only idea we have without using foam.

As for places of stagnant water, that is going to happen, it is unavoidable. The backsides of the rock for example that are buried in the foam (for those designs that use it). I have some seriously open channeled rock from BRS, and that stuff could easily capture debris. So blowing out the rocks will likely wind up on the maintenance schedule, but what can you do? It is no different than having rocks just piled on top of each other, debris collects in places unfortunately.