Heavy Rock????

[TehTANK]

I am looking to put many stones into my tank and have a large cave for my Oscar to go into. I am worried though that all the stone in the tank will be to much weight for the bottom and it will crack or not hold. Is this true? Is that to much weight for the bottom of the tank?

Plus cleaning....when you have to remove all that rock and what not..does that put stress on the glass and what not?

Anyone out there that has a lot of large stones in their tank to make a great Cave?

[Abbeys_Mom]

The heaviest rock I put in my 55g tank was 5 pounds (it was sitting in my front hall, so I popped it on the scale. It was not the only rock. I would say that there was at least 50 pounds worth of rock and gravel in the tank. So long as the tank is properly supported (not sitting just on the frame, or just on the bottom glass) and is level. It should be ok. It also helps to have the weight distributed evenly. Heaviest items should be on the edges of the tank, not stuck in the middle.

[Fishguy2727]

The best thing you can do if looking into a lot of weight, put an egg crate on the glass (white plastic light diffuser with all the little 0.5" squares), then pile on the gravel. This distributes the weight acorss the entire bottom, ratehr than just a few points. The rock should be put on the egg crate, not just the gravel. This helps prevent the rock from shifting from the fish digging under it. This is how I have my 150 setup, and I have a lot of rock in there, well over 100 pounds.

[Lady Hobbs]

Very good answers here to a problem I also was wondering about.

[TehTANK]

Thanks for all the advice. I like the egg crate idea. I am thinking of doing through out the whole bottom of the tank to help from scratching the bottom of the tank as well. I feel safe putting in some rock now.

Thanks again

[Fishguy2727]

Thats how it should be done, across the whole bottom of the tank. You will probably need to cut the egg crate down to size. I used wire cutters for this. Make sure the entire egg crate is sitting on the glass, that none of it is up off the glass, resting on the silicone. It needs to be flat on the bottom. The plastic of the egg crate has an almost neutral buoyancy, so it is a good idea to put a rock on it to hold it down on the glass, then add your sand or gravel. Otherwise you could end up with some between the glass and egg crate.

[Abbeys_Mom]

I was luck with my "stand" for my 55g, I used milk crates to hold it up. The crate fit perfectly under the aquarium (touching the glass) and I used a metal frame (same size as the outer edge of the tank) on top of the crates for extra stability. The frame fit snuggly over the milk crates to make the whole thing level (because milk crates are made to stack and have a lip on the outer edge). It's worked great for 10 years. I just draped black fabric across the front so you would never know they were under there.

[TehTANK]

Question though. I do not have crate in the bottom of my tank yet but would like to put that in there. Right now I have small rock at the bottom of the tank. Is there any way to get the crate in there with out having to empty all the rock out so that way there is no rock between the glass and the crate?

[crackatinny]

I overcame this problem by using the base part of an undergravel filter to even out the weight

[Lady Hobbs]

Why couldn't a person use a whole sheet of syrofoam and just cut it to size before adding the gravel? Actually, syrofoam or pegboard should also be used under the aquarium to give a bit of cushion for uneven flooring.

[Lady Hobbs]

TehTANK....you have asked an excellent question here and one that probably should have been addressed previously. I had not thought of it at all until I saw that picture of "floored" tank and all those heavy blocks in one area. That would cause me some concern, I think, so glad you brought this topic up.

[Fishguy2727]

Not really an effective way of installing it with gravel in the tank. You may have to remove the gravel and do it.

[f1oored]

The glass on the bottom of the tank is pretty thick and very tempered. As long as your tank is sitting flat and you aren't dropping the rocks in from four feet up you should be fine. I have almost 80lbs of big rocks and 25lbs of gravel without the egg crate and my glass isn't breaking. The egg crate is still a good idea because it keeps the rocks steady when the fish dig but I think your tank would be alright without it too. But a wise man would error on the side of safety right?!? lol

[Glasstapper]

Oh, I was actually wondering about this, too, when I would see huge rock formations in cichlid tanks. I figured it was something like the egg crate stuff you put on your bed, but I didn't know if it was just under the rocks or under the entire substrate.

This is very handy info. Thanks.

[kimmers318]

Which leads to another question...what exactly do you guys mean by egg crate....I have seen the foam bedding called egg crate...or are you getting the styrofoam egg crates like what actual eggs come in? I worry about my husbands mbuna tank with all of his rock work, but that is just me...a worrywart....he doesn't have a care in the world. I am forever getting this mental picture of the bottom of the tank cracking, and me running around trying to bucket his fish before the tank runs out of water! Thank goodness we have a slab home!

[jeffs99dime]

you could mix in false rocks (plastic) to save weight too.

[Fishguy2727]

The egg crate actually has nothing to do with eggs. It is a plastic light diffuser that goes over standard fluorescent light fixtures (the ones that sit up in the ceiling). They have a bunch of hollow squares in them. They are also used as heavy duty tank dividers. The squares are about half an inch. They are in the lighting section at the bigger hardware/home improvement store.

[MrKickalot]

I read somewhere that weight isn't as much of a problem as long as there is something to distribute it. It said a thick bed of gravel. If you think about it the water displaced by the rocks will probably be almost as heavy as the rocks themselves (depending on what kind of rocks of course). You might think you are adding 100 lbs to the tank but if they displace 8 gallons of water you only added 36 lbs. Like I said as long as the weight is distributes across a large area it should be fine!! I like the egg crate idea though... if I redo my tank and put a large rock formation in it I might try that!!

[Fishguy2727]

The egg crate will distribute the weight across the entire bottom. A thick bed of gravel (besides being avoide din the first place to prevent the buildup of debris that leads to soaring nitrates) will at best distribute it to slightly larger area. With any fish that will be digging, that thick bed will become a crater in no time. and since they usually like to dig next to rockwork, that rockwork needs a base to sit on. I consider the egg crate to be almost a must for any tank. It won't hurt anything and it can only help prevent problems, even small problems such as a scratched up bottom.

[f1oored]

A glass tank that is fully tempered will break at 15,000 PSI. If you want to add 100lbs of rock to your tank you must (if my math is correct) make those rocks contact at least .007 square inches of your tank bottom. That is if you take 1 square inch and divide it into 1000 units, your rocks must touch at least 7 of those units. This is of course if your tank is fully tempered glass.

If your tank is annealed (also common for aquariums) it will only withstand 400 PSI. This means your 100lbs of rock must make contact with 1/4 of a square inch before they will break the glass.

[TehTANK]

Here is the thing though....anyone making a rock formation is usually doing it on one side of the tank and it means that many rocks are stacked on top of eachother. My worry was to much weight on one side of the tank or glass. Also that puts a lot of preassure on different contact points in the tank. The egg crate is a great idea and I am going to get some tonight and put it in my tank for sure. I am not going to build the rock formation up yet. I still have to get the rock but I was more concerned of so much weight being on only half of the tank. I was going for a look fo rock on one side and drift wood on the other with lots of plants around all of it so my oscar would have lots of fun things to play with and feel safe hidden anywhere in the tank. What do you guys and girls think and also about the rock all stacked up on one half of the tank????

[Abbeys_Mom]

I think it would be ok. If it is for an oscar tank I would suggest attacking the rocks together into a formation before putting them in the tank. I know my oscar could move large rock with little effort. I would hate to think of the tank breaking from a falling rock. I have heard a few horror stories of oscars smashing the glass in aquariums.

[TehTANK]

Great idea! thanks for the advice. Anyone know what I should get to do that?

[Abbeys_Mom]

I wonder if you could use the stuff you reseal tanks with to stick rocks together? It would have to be safe for aquarium since it goes on the inside. The question would be if it would hold the rocks together.

[f1oored]

Stack of rocks on one side with drift wood on the other...

http://i24.photobucket.com/albums/c45/f1oored/tank033.jpg

That is about 80lbs of sandstone if you are wondering, with no "egg crate" and only a thin layer of substrate. With the egg crate you could likely fill the entire tank with rocks.
Just stop worrying, your tank is going to be fine.

I would glue the rock together before putting them in the tank (maybe in sections that aren't too heavy). Abbeys Mom is right, that will give you better stability

[crackatinny]

I would use aquarium grade silicon to glue rocks with, if it holds the glass together under the pressure it is under, I cant see why I would not hold the rocks in place

[NorthernBoy]

You can as crackatinny says use silicon. although if you glue then it will be difficult to clean betweem the rocks. I have used flatter rocks with very broad sides. Instead if egg crate i put about a half inch on sand/aragonite mix than placed flat stones covering most of the bottom of the tank. Fill in the space between with more sand/aragonite mix. (like tiles) Then build atop the broad base. The weight is dispersed well and the rocks will help protect the bottom of the tank fron falling stones.

[TehTANK]

Thanks so much for all the ideas. I will use them all and I am going to get some rock for the inside. Thanks for the pick F1oor. It is awesome and kind of the same look I am going for. I will probably use egg crate and glue them together. Thanks so much guys! This has been so useful. Now a question....What kind of rock would be good to use?????

[f1oored]

What kind of fish are you going to keep?

[Fishguy2727]

A lot of rockwork and woodwork in a high waste (oscars) tank can be a big problem. Oscars are not the cleanest fish and all that decor can end up catching a lot of debris. This can lead to water quality issues. My jaguar cichlid's tank only has a T-connector for 6" PVC pipe. It works great and he loves it. There is also effectively no dead spots to catch debris. The look can be hidden by attaching decor to the pipe.

[TehTANK]

I understand about them being messy fishies and that changing my water quality. As much as I do water changes though and as often as I clean I am not to worried about it. This has been my dream tank and I cant even begin to tell you how excited I am to finally get it put together the way it has been laid out in my head all these years. I appreciate the advice.

I am going to have 2 oscars in there and a couple of bottom feeders I am sure. Right now I have a large oscar in there and a small one. I just got the small one so he needs time to grow. I have a cory as well that is bloated right now. I am sure if you know if you have been reading other parts of the forum. So the answer is 2 Oscars.

What do you suggest for rock?

[Fishguy2727]

Any rock that you like that does not buffer the water at all should be fine. I would also avoid rough stuff like red lava rock. Many can buffer the water: lace, Z-lite, antique coral, tufa, and I think travertine.

[TehTANK]

So what kind of stone would you think would be good???? Anyone????

If I were to go out and find a bunch of big rocks out of the ground and wash them up real good and let them soak in a bleach bath for a little while and then washed them again.....do you think that would hurt anything?

[Fishguy2727]

I really like my red sandstoen chunks. I think Feller Stone sells them as deert red. Other sandstones would be good as well, liek the rainbow sandstoen that you can get as big chunks or carved (with all th ehole sin it, even though the oscar won;t fit through them). Go to Feller Stone's website and see what you like. If your LFS can get any Feller stone they should be able to special order any type by the box, which would be good for a large tank.

[Lady Hobbs]

No one answered me but is there any reason a big square of styrofoam can't be used under the gravel?

I don't think I'd glue stones together. What happens if the glue gives way about the time you're trying to pick it up to clean? One may fall to the bottom breaking the tank. I think I would use either fake stone as suggested by jeffs99dime or flat slat. Just my 2 cents.

[Lady Hobbs]

Hey TehTank......check your messages.

[Incredulous_Ed]

Slate seems to be on of the best aquarium rocks. most all of the aquarium books i read said to glue large rocks together with silicone sealent. One book had a 100 lb peice of rock! to support it, the tank had fine sand as the subsrtate

[jeffs99dime]

No one answered me but is there any reason a big square of styrofoam can't be used under the gravel?

I don't think I'd glue stones together. What happens if the glue gives way about the time you're trying to pick it up to clean? One may fall to the bottom breaking the tank. I think I would use either fake stone as suggested by jeffs99dime or flat slat. Just my 2 cents.

are you referring to the white, packing foam?

[Fishguy2727]

I would not use foam. The egg crate works great. The foam would probably be crushed, as well as distructive species that like to dig may expose it and then tear it up, leading to a nasty mess. Not to mention I would not put money on foam being chemically inert.

[MrKickalot]

I love math heads!!!


A glass tank that is fully tempered will break at 15,000 PSI. If you want to add 100lbs of rock to your tank you must (if my math is correct) make those rocks contact at least .007 square inches of your tank bottom. That is if you take 1 square inch and divide it into 1000 units, your rocks must touch at least 7 of those units. This is of course if your tank is fully tempered glass.

If your tank is annealed (also common for aquariums) it will only withstand 400 PSI. This means your 100lbs of rock must make contact with 1/4 of a square inch before they will break the glass.

[f1oored]

Tank

Get some vinegar and head off to your local landscaping store. Forget the LFS for tank rocks. The last thing you want to do is pay $2.50 a pound when you need 100 pounds of rocks.

Many landscaping stores have various types of rocks for 10 - 20 cents per pound. I got all the rocks in my tank for 14 bucks. Pour a little vinegar on the rocks you want, if they bubble they are no good. If they don't bubble you can use them most likely.

Clean them with bleach (low concentration) and then let them soak in a bucket. Check the water in the bucket after a week or so to see if the rock has changed any of the values. If the water is good then so is the rock.

And one last very important thing to remember. Take pictures along the way so we can see your work in progress. Good luck

[TehTANK]

Tank

Get some vinegar and head off to your local landscaping store. Forget the LFS for tank rocks. The last thing you want to do is pay $2.50 a pound when you need 100 pounds of rocks.

Many landscaping stores have various types of rocks for 10 - 20 cents per pound. I got all the rocks in my tank for 14 bucks. Pour a little vinegar on the rocks you want, if they bubble they are no good. If they don't bubble you can use them most likely.

Clean them with bleach (low concentration) and then let them soak in a bucket. Check the water in the bucket after a week or so to see if the rock has changed any of the values. If the water is good then so is the rock.

And one last very important thing to remember. Take pictures along the way so we can see your work in progress. Good luck


I will make sure to take pictures. Thanks for the advice. I will do the vinegar test. I have my dad getting some stones from his place as well that I plan on soaking. What do you mean by check the water levels??? I am confused...sorry.... I can't wait till I get it just the way I want!

[Fishguy2727]

He means to check things like pH and hardness after the rock has been soaking in the bucket for a while to double check that it won't screw with that kind of stuff when it's in the tank.

[f1oored]

' /\
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Yes, what he said.

[TehTANK]

Alright that is what I will do. Thanks again guys. I can't wait till I get it completed!

[TehTANK]

Well I went out and bought a sheet of the egg crate. Tonight I have to find a way to get it under my substrate without having to pull all the rocks out and what not. That should be fun. It wasn't to bad. $10.50 for a sheet. I had to get some snuips though to cut it and that was another 10$ or so. Little by little though it is getting there. I have to soak it tonight though to make sure everything is off of it. It felt a little dusty and oily last night when I bought it.

[NorthernBoy]

Most landscaping companies have fancy names for common rocks and minerals. The ones I use are; Minnesota and Pennsylvania Bluestone, and common Flagstone. They are both sandstone/mudstones (sand and mud refer to the size of the grain of sand in the rock not the composition) Go to the landscaping company and as for a "random pieces" bin. I pick mine out of there and pay $0.10 per pound and they are usually smaller flat pieces that can't be used for paving anymore because they are too small. You can ask the owner/head manager of the landscape company about the rock too. Good questions include: 1) are these rocks calcite/calcate based rock? (they will raise pH) 2) are there any metals or minerals that will oxidize or leach out into the water from these rock?
Another resource I use is the local quarry. I use limestone as a buffer in my tank as well and it is mined just down the street in the form of dolomite. Dolomite is a great buffer for aquariums because it is usually formed in the ocean from pieces of reef and shells. Good luck and enjoy setting up your tank! Exploring options and finding out new things about aquascaping is one of my favorite parts of the hobby. What ever you do I am sure your tank will be great.

[TehTANK]

Thanks Northernboy. That is great information. I think I am going to print this out and head out and see what I can find. Very helpful. I will make sure to post pictures when I get everything the way I want.

[jeffs99dime]

for attaching the rocks to each other you could also use "marine grade screws" basically they're just stainless steel but they're rated for marine use. i have used them several times before on differnt jobs that i've done. they work great.

[TehTANK]

Well I put the egg crate in this weekend. Went in great. I soaked it and washed it real well to make sure there was nothing on it. I cut it into to pieces and then moved all the rocks to one side of the tank and put t down and covered it and then I did the same thing to the other side. you can't even see it in the bottom of the tank. I feel much better putting my stuff in there now and just cant wait to get the rock in there when I get the money to get it. Anyway, Just wanted to say it works great and I would suggest it for anyone's tank because it really does protect the glass.

[Lady Hobbs]

yea ....tehTank. Glad you gott'er done! Now you can move onto the next challenge. NorthernBoy gave you some good information on rock. Hope you can find just what you want.