How stable is stable enough?

Cruz Mc5 · Nov 29, 2018

I can’t really find a good answer for this. I’m setting up my first tank. I’ve got my rocks set the way I like them, but they are a little unsteady (can rock back and forth a little bit). I’ve epoxied some together, but am trying to keep from using epoxy on all of them just in case I need to get some of them out.

Obviously, one solid piece would be the best stability wise, but that would make it tough to pull the rocks out if needed. And it would mean placing one huge rock in the tank which could be tough.

Since that’s not recommended, how stable do you need to make the rocks. Can they move back and forth a little bit? Is that going to cause problems later on or risk falling? Should I use epoxy on some and then plastic rods on the rest?

Any help or guidance would be appreciated!

cracker · Nov 29, 2018

Iv'e heard 5 points one way or the other. I find this narrow range difficult. Here's a bump for Ya

KrisReef · Nov 29, 2018

Sounds like a physics question and without more knowledge on the tanks current acceleration, angular momentum, Renolds number, the coefficient of friction of the rocks you are stacking I'm afraid I could only guess if you need more rods, etc?

But for a general rule of thumb, if it threatens to tip over or collapse everytime you want to do tank maintenance then it needs more stability.

And if you stack things so loosely that it caves in on your prized fish, (don't ask) you will wish you used more adhesive.

It is a good idea that it be moveable for maintenance, or re-scaping later, so I am not certain there is a hard a fast rule on how stable these things should be?

I hope my chatter helps at least gets the conversation started.

WV Reefer · Nov 29, 2018

Cruz Mc5 said:
I can’t really find a good answer for this. I’m setting up my first tank. I’ve got my rocks set the way I like them, but they are a little unsteady (can rock back and forth a little bit). I’ve epoxied some together, but am trying to keep from using epoxy on all of them just in case I need to get some of them out.

Obviously, one solid piece would be the best stability wise, but that would make it tough to pull the rocks out if needed. And it would mean placing one huge rock in the tank which could be tough.

Since that’s not recommended, how stable do you need to make the rocks. Can they move back and forth a little bit? Is that going to cause problems later on or risk falling? Should I use epoxy on some and then plastic rods on the rest?

Any help or guidance would be appreciated!

A little movement is mostly ok. Just keep that in mind when buying certain fish or inverts that may hide in and under the rocks.

Billldg · Nov 29, 2018

I just try to use common sense when I put my rock in. I figured that when I pushed on the rock in several different directions, if it wiggled it wasn't solid enough of a foundation. If their was a big enough overhang then I pinned it with a rod.

TheOneWhoIsThere · Nov 29, 2018

I’d keep it as stable as possible. One of my rocks fell, it caused no damage but I had to rearrange my aquascape a little bit. If it has a low chance at falling, it probably will, well I guess it isn’t a low chance then.

Cruz Mc5 · Nov 29, 2018

Hmmm. I couldn’t get the coefficient of friction for my rocks. Apparently it’s not a common measurement for them. And the acceleration of the tank itself is zero, but I imagine the water inside is going to change fairly often. Where’s Will Hunting when you need him.

Sounds like I should probably do something to make it more base is very solid, but the next layer can rock back and forth. I’m just not sure about what forces the rock is typically exposed to in a reef tank.

naterealbig · Nov 29, 2018

I've seen some use zip ties to hold rock together. Just cut the tie when you need to move the rock.

It will look funny at first, but the zip ties will grow stuff on them, even Coraline. Perhaps you could try this.

If they move a little it's fine. If a large rock is easily tipped during maintenance, it may be more of an issue.

Assuming you have sand, it may be a good idea to push the base rocks down far enough so that they are sitting on the glass. This will prevent sand movement from causing the rocks to shift.

Hope this helps!

Cruz Mc5 · Nov 29, 2018

My plan is to put the rocks in first and then use sand around them, so the base level will be on the glass. My main concern is for the next levels of rock. They’ll be solid if I epoxy them to the base rocks, but then it’ll be impossible to take them out without removing the whole structure.