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I have been given some awesome quartz, granite and flint rocks for my tank that are about up to 10 pounds in weight each.

How can I put them in my tank without stressing the bottom glass, please?

I thought of a sheet of plexiglass under the gravel to help distribute the weight.
Is that a solution?
How thick should it be?

ANY help would be greatly appreciated, Please!

Hi,
Take all the substrate out of the tank, lay down what
is called plastic "Egg crate" on the bottom, and then add
substrate to the desired depth. The egg crate will
distribute the weight of the rocks across the entire base
of the tank, and also prevent the sharp edges or bumps on
the bottoms of the rocks from sitting directly on
the glass.
The bumps and points of the rocks concentrate the weight
at those contact points with the glass and cause stress
fractures over time.

You can get the egg crate from Home Depot and the like.
It is the slang term given to the sheets of plastic that
are mounted in overhead lighting to distribute the light
into the room below.
http://www.edee.com/eggcrate.htm

Just setting the rocks around in the tank on the substrate
can work, but over time, the fish digging around the rocks
and your cleaning can cause the rocks to settle down
through the gravel to rest on the glass where the points
and bumps cause the problems. Also any odd shaped rocks
can tip over and possibly crack the glass.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Great!
Thanks So much, Frank.
That is an Awesome solution!

I Really appreciate your experienced advice, friend.

Don (dS)

Frank beat me to that answer but I would also add a 3/4ins thick styrene foam base "under" the tank this will also help spread the total weight over the tank stand.

Also be extremely careful when placing the large stones into the tank it only takes one scratch and you can guarantee not far down the track you will have a cracked tank.
Remember to fix them firmly into the substrate not just sitting on the top where they can be easily knocked over when you are working in the tank.

Have a look in [link=My Profile] http://www.fishprofiles.com/forums/member.aspx?id=1935[/link] for my tank info
Look here for my
Betta 11Gal Desktop & Placidity 5ft Community Tank Photos

Keith

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Thanks guys,
I'll look into getting some styrofoam padding. Thanks!

But now I'm leaning back towards the plexiglass (and foam) idea again...mostly because it seems to me that the "squares" would be traps for fish waste and excess food (what little I give them)..and be a really problem with syphoning and cleaning, etc.

Wouldn't the rocks on plexiglass with foam under it distribute the weight(under the substrate), not allow glass scratching and be Much easier to clean out, when needed than all the small compartments of the egg crate?

Found something I'll use that is more for fishtanks than styrofoam. I was uneasy about "chemicals" in styrofoam, so I've order some of this to put under the plexiglass holding the large pile of rocks and more evenly distribute weight:

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=13965

thanks everyone for helping me work thru this solution!

To my knowledge styrofoam goes under the tank, not in the tank, reducing the pressure by equalizing the weight on the glass.

The product you linked to looks to me more like a mesh like material, filter media really, I dont' see that distributing the weigh of the rocks, just protecting the glass of the tank a bit from any sharp points on the rock. You need something stiff like the egg crates.

My one bit of advice is to hold onto the rock carefully as you lower it into the tank. Somehow I lost control of one rock and my heart was racing as I dug around trying to see if there was any damage!

^_^

Yes Babelfish, that sounds good, but there is NO WAY now that the tank is full of about 50 large fish and water to put styrofoam under the glass. If I had thought that I would have large rocks in the tank (which have mostly all been given to me by friends, after the tank was full and housing the fish)...initially, I would have really appreciated knowing about and doing that. Thank you. That was a good idea to be under the glass.

That stuff I'm buying IS some bio-filter media that comes in large colored sheets, and 1/2" thick, the same black color as my substrate and is somewhat slightly compressable. I also bought it because it is something that is made to be compatible with aquarium water chemistry.
It is very slightly "spungy". And I still think egg crate will confine waste, etc. in the 1" squares and be a chore to keep from gasing waste gases, if I don't syphon the squares out very, very frequently...which I'd rather not need to do so often.

Here's my plan:
1)One side of the tank at a time, while the fish have moved to the far side...remove all the substrate, silk plants, etc. down to the glass.
2) cut the Slightly Compressable sheets of 1/2 " thich black bio-media into 18"(tank depth)x 24" long pieces...then lay it on the glass.
3) put a 3/8" thick pane of plexiglass on top of it, cut to about 17 1/2" x 24".
4) put the black gravel substrate on top of the plexiglass sheet(s)
5) then arrange the rocks on top with the silk plants again.

Does that not sound good?
The plexiglass sheet(s) will take the "scratching" (not the glass)...and the weight will be distributed around by the moderately compressable media under the plexiglass(the plexiglass will bend slightly in areas of weight depending on size of the various rock placements and be cushioned by the slightly compressable black media material under it).

Does that sound OK, guys??

Hi,
Actually, No, the padding inside the tank is not a good
idea. In essence, you will be creating a huge sump, a
huge anaerobic area of bacteria that eventually will
poison the tank. That bulk padding is for "Do-it-yourselfers"
so that they can purchase bulk filter pad, cut it to size
and use it in their aquarium filters. It needs to be
oxygenated (water flowing through it). It is far less
expensive than purchasing the precut stuff from the
filter manufacturer.

The Egg crate is still the best way to go to protect
the entire bottom of the tank. When using it, you do need
to use a siphon such as the Python brand to clean the
gravel down to the bottom of the tank. But then, you have
to do that in any tank, anyway.

If you are going to use only a few rocks, here and there,
then a small piece of Plexiglas siliconed to the bottom of
each rock as a base, would also work. The piece should
no larger than than the rock, glued to the rock, and
the whole assembly, when properly cured (dried)
set directly on the glass bottom (clear away the
gravel) and then the gravel filled back in around
the rock.
The Plexiglas will provide some stability, and protect
the bottom from pressure (stress cracks), and
distribute some of the weight over a larger area.
A whole plate of Plexiglas is not a good idea as it
too will leave gaps between the bottom and the sheet,
and form anaerobic areas.

Some folks will use the styrofoam that has been mentioned
as a mat, between the tank itself and the stand the tank
is to be set on. The idea is that if the tank stand is
wood and not perfectly smooth and level, that it can
present high spots, and low spots that would allow a filled
tank to settle and in the process to settling into the
uneven spots, torque the tank. The torquing of the tank
places great stress on the siliconed joints which can then
stretch open and leak.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Frank,
I have maybe 80 rocks of different types, shapes and sizes/weights.
Some of the larger ones will be "stand alones", others will be loosly piled of diferrent shapes and sizes to make more hiding places for some smaller fish, besides the many artificial plants.

Some of the smaller rocks are already siliconed together as a tunnel/cave (about 14" long by 10" wide)for bottom fish to hide out in. That tunnel alone weighs about 30 pounds (13.6 kg). It itself has it's weight spead over the length of the the two 14" side bottoms.

I would estimate the combined weight of various single large rocks, medium size rocks in piles and siliconed rock structures to be about 250 lbs(113 kg), plus the 65 lbs (29 kg) of gravel/substrate already in the tank.

That is the situation divided between both ends of my 125g. tank with a few larger "stand alone" rocks near the center of tank near the back wall.

Lots of rocks.

thoughts?

Hi,
Should be fine, especially if spread out across the tank
and up against the back. "Loosly Piled" is never a good
idea, sooner or later, for various reasons, the piles fall
down, sometimes squishing fish, or smacking up against the
glass.
I'd silicone, or epoxy the "loose" ones together.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Thanks Frank,
I'll remember that!

Frank,
I understand your concern about the filter media under the plexiglass, but really how would hardly anything filter thru the substrate and get thru the plexiglass to it?

Let me mention a couple other things about this big tank setup, please also.
I do frequent water changes, Do not like thick substrate because "stuff" filters thru it to the bottom, as you know, and stays there until disturbed/removed. I only have about 3/4 inch of substrate over the bottom, for that very reason. And would need to add more if using egg crate.

And I have a few good sized active SA Eartheaters that are constantly turning it over. Nearly all of what is there when they turn over the substrate down to the glass, gets filtered and trapped in my 3 massive HOB powerfilters that cycle the whole tank about every 6 minutes. The thicker substrate and plastic egg crating would negate that by the eartheaters.

And there is a current running thru the tank caused by a huge powerhead/UV Sterilizer combination that is rated for 4400 gallon ponds that pulls water in from one end of the tank...under the tank to the sterilizer..and then shoots the water current out from the opposite end of the tank (the fish all seem to love it, as if they were back in their streams and rivers again).

How would "poison" collect if nothing got thru the plexiglass and with that filtration, sterilization and frequent water changes?

Frank,
What about THIS idea?
I so much do not want to go thru the trouble of cleaning every single egg crate square....how about putting egg crate on the glass on the bottom of the tank (no filter media)..with a cut to-size plexiglass sheet siliconed to the top of the egg crate....so NO substrate would get in the wholes/squares?
(the substrate and rocks on top)

How does that sound, friend?

Hi,
(Back in town)

Your two earlier posts kinda negate the use of the egg
crate lining. My assumption was that your substrate depth
was around 3-4 inches. With just 3/4 of an inch I'd skip
using the egg crate.
Generally speaking the egg crate is what is used to provide
a support for the rocks spreading the weight across the
bottom and preventing the rocks from pressing on the bottom
glass. Changing the substrate depth to 1 inch vs 3/4 would
not do any "damage" to your criteria. The Earth Movers,
however, would soon expose the egg crate making it a possible
eyesore. As for just setting the rocks on the substrate
alone, those fish would soon undermine the rocks and cause
them to shift. That, of course, would cause problems if
the rocks are just setting atop one another.

Your original question, and replies were aimed at safely
distributing the weight, and cushioning the bottom glass
from the sharp points and bumps of the individual rocks
that could cause stress cracks in the bottom glass.

Placing the rocks on small pieces of Plexiglas on the glass
bottom would be another option. Siliconing the rock to the
Plexiglas and then setting the assembly on the clean tank
bottom is an option. I'd steer clear of a cut to size
piece of Plexiglas that covers the entire tank. I don't
like the idea of any trapped water between the tank and
the lining, that could be a problem.

Placing the egg crate with a sheet of Plexiglas glued to it
on top of the squares could provide a terrible area of
anaerobic bacteria. Any water that got into the squares
would be trapped with no circulation and go "stale."

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

What about an under gravel filter plan under the rocks? Wouldn't this spread the weight out and keep water moving under the rocks if it was running?

Thanks Frank,
I was Not going to cover the whole tank botton with a plexiglass sheet...only where the larger rocks will be.

I guess I'll just silicone the rock/rock piles to small pieces of plexiglass then. Thank you for your interest and knowledgable responces to my situation.

Gourami,
Friends of mine have suggested rocks on an undergravel filter, but I truly dislike that kind of filter because of it's need to be periodically torn down to clean them. I appreciate your thought though. That of course would work if I didn't dislike undergravel filters.

Thanks All,
dS