View Full Version : stacking rocks
sorry, this is posted in reefkeepers too. i wasn't sure who would know the answer better.........
stacking rocks
i know you need something under them to prevent pressure points....
but what about the sides?
up until now i have always made free-standing piles of rocks, is it ok to let them touch the sides of the tank or even stack against it?
TIA
thom336
06-28-2003, 10:16 AM
I wouldnt stack the rocks against glass, as the pressure would weaken it over time. Having sand as a substrate reduces the pressure of the rocks on the base. I wouldnt stack them free-standing, instead if it is to be a more perminant fixture in the tank (which I am rather assuming it will) then I would secure the main pieces together with a silicon sealant, smaller pieces could be placed loosely around, as then there is little chance of it all toppling over - which would shatter the glass.
Im not the most knowledgable about stacking rocks, and you probably would have better luck with a detailed answer in marines.
Good luck!
Thom.
Rocks should never be stacked on sand or gravel - that is asking for the stack to topple. Vacuuming, a digging fish or invert, etc., can undermine such construction. Rocks need to be built up over a firm base. I use eggcrate light diffuser and/or blueboard styrofoam. Either will diffuse pressure points and protect the bottom glass.
If you are building a major structure, build by the same priciple by which dry stone walls are built: Two over one, one over two. That means that if you have two smaller rocks, you bridge over both in the next layer with one larger rock. If you have a large rock, it should be supported by two (or more) smaller rocks. The larger rock can in turn support two smaller ones in the next layer, but they should be secured in the next layer with larger ones, bridging to each side, not a vertical stack. "Stacking" is exactly what you do not want, what you want is to almost weave the structure together with rock.
My mbuna tank was set up in this manner, several hundred pounds of rock, all the way to the water surface in the back. It never shifted in the approx. 15 years it was set. At the rear of the tank, a strip of eggcrate protected the back glass from scratches and pressure points, ending below the top row of rocks which did not touch the glass.
If you have never looked at a fieldstone wall, study one some time - a huge range of sizes and shapes, all tied together without morter and stable for decades at least. You just don't want it that regular and flat across the front.
Using aquarium safe epoxy to stabilize that stack will help a great deal.
JSchmidt
07-07-2003, 1:09 PM
I've not found epoxy or silicone to hold that well with most rocks... it always seems to hold for a while, then starts to give. I'd rather put my faith in stable stacking. For me, that includes most of what RTR noted. I use a variety of things below the rock to safeguard the glass: slate sheets, foam, and lately, sheets of plexiglass. I never add substrate (sand, crushed coral) until the rocks are in place and stable. I check the rock piles regularly to guard against shifting.
I also have stopped gluing rocks together because I find it disinclines me from tearing down and cleaning the tank. Even if you only tear down a tank every year or two, it's much more of a chore if the rocks are glued together...
Jim
I agree with piling them in a stable stack. I think it would be added insurance to epoxy them together. BTW, if it is good two part epoxy that has been allowed to cure at room temps for at least a week, it shouldn't break down.
kveeti
07-07-2003, 10:29 PM
Piling rocks in a stable stack reminds me of this cool rock-person somebody built at Rocky Point at the cottage...
http://members.shaw.ca/pcarriere/rocks.jpg
I wouldn't trust my own stacking ability over 2 high.
LOL, cool pic!
i probably should have specified they were lace rock, so glueing isn't a real good option. not to mention they lock together pretty good to begin with. it's a 55g so it's only 12" wide. so i have a fairly nice pile at the bottom but it tapers up. i wanted to go wider, higher so i could add more rocks, but that doesn't really seem practical unless i allow some of the rocks to contact the back glass........ maybe i'll try the eggcrate, but it seems like that could look pretty hideous....
thanks :)
The eggcrate goes first, then the stacked rocks, then the gravel.
not like that matak.... i meant on the back wall of the aquarium. to distribute the load of the rocks, so there is no pressure points.
i knew what he meant. :D
thanks :)
Sumpin'fishy
07-08-2003, 11:59 AM
Personally I think plexi-glass (Acrylic) is better at distributing weight and also doesn't have the negative looks and other features of eggcrate! If you think about it, a solid, smooth surface is better at distributin weight, than an interlocking network of plastic plates with large areas missing. There is always the possibility (although minor) of sand becoming anaerobic within these open squares between the eggcrate. Also, eggcrate is hideous to look at in any kind of display tank!
1/4" of plexi is more than enough to keep the bottom (and any other sides) of the tank from having excessive pressure forming against small areas (pressure points). If you use it on the bottom of the tank (like I do), just add the plexi first, then add the sand. Make sure no sand gets between the plexi and the tank bottom, and you will never get any scratches on the protected area. Plexi is also more durable, yet pliable than glass, so it won't crack itself when heavy rocks are stacked on it. It will get scratched easy and get minor pits and dents in it, but WHO CARES!
I personally cut mine about 1/2" less than the overall inside dimensions of the surface I'm protecting, that way it fits snug without overlapping the silicone bead around the edges. You can then silicone it in place, if you like or not. I did not silicone mine and just laid the sand on top of it. I have had no problems at all, and I have large pieces of Limestone in my tank. Just for the record, I do have two rocks that are positioned more vertically than horizontally, and they lean against the rear glass, I am very careful not to push against these rocks when moving things around. If I decide to do anything to protect the rear glass, I will simply add a sheet of plexi (1/8" would probably do fine).
The eggcrate in my mbuna tank was completely invisible - the base was covered with gravel, The back wall with rocks. Not an issue IMHO. There werw no anaerobic areas at all when I broke it down after ~15 years.
Eggcrate is stronger and more rigid than 1/4" plexi by a wide margin, so would distribute the load/pressure points over a wider area, but either should do. Styro will do as well, and it is not strong. Likely it is all personal choice so long as there is some protection against pressure points with massive weight.