Rocks Rock.....Don't let them Roll

So you've decided on a Rift Lake tank and will be keeping rock loving cichlids. What better idea is there then to use real rocks to provide them a comfortable home. Seems simple enough and it really is. However, some things should be kept in mind when building that perfect stone castle for your fishy friends.

Rock collection and type.

For some of us collecting rock is just a walk in the backyard or a trip down the road. When collecting "free" rock make sure you have the permission of the land owner and check with your local Government offices as to any collection laws they may have for public use land. You don't want to end up in jail explaining to a professional thief how you got caught stealing granite for your aquarium. You will have no cache.

OK, you have "permission" and you are out to hunt down that elusive, perfect rock. Something to watch out for is the wild life. Wear gloves and carry a stick to poke around that stone before you try to remove it. Some of the things you could run into are rattlesnakes, scorpions, venomous insects and ticked off ground squirrels. Make sure nobody is home before picking your rock up.

Some of the rock you want to avoid are clay like rocks such as calichi which have smaller stones mixed in with it. Most likely it will break down in the aquarium. Also avoid any rock that has rust or heavy blue or green miniral deposits. Better to move on down the line to find "clean" rock.
Granites, basalts, and everything inbetween are good choices. If your fortunate enough to live in an area with limestone deposits these also make good additions to the aquarium and have the added benefit of helping to buffer the water. Most slates and hard sandstones can also be used. As was mentioned earlier, avoid anything that looks like it has heavy mineral deposits and avoid shale that comes from areas of possible oil reserve. Lava rock can also be used but be aware that some of it can contain very high metal and mineral content. The basalt of one of the Hawaiin island is one of the hardest stones around but high iron content and weathering cause it to eventually break down like bread crumbs.

Another option is to buy it from a Lfs or from a place that specialises in stone. All the same rules apply.

Choosing the shape and size of the rock is also important. Smooth river stones are beautiful to look at and make a very nice display. Make sure that you pick river rock that is flattened and not overly round. They will be much easier to stack. The granites and basalts are excellant choices and normally break along clean flat plains. Limestone such as "Holeyrock" can be broken and shaped rather easilly but imo look best when large peices are used along with a few smaller structures to fill in. Classic lava rock is generally rounded but their rough nature helps lock them in place when stacked.

Whatever stone you decide to use make sure you collect different sizes. A couple of large peices with medium peices stacked around it gives a more natural look. Don't forget to collect a lot of the much smaller pieces also. These come in real handy to use as "chinkers" to fill in that odd spot for support and/or to place around your stack to give it that complete look.

When you think you have enough to fill you tank collect a lot more. The more choice you have in size and shape the better and easier it will be to make your stacks.

So you come home from a successful hunt and you have more stones then you can possibly use..... What's next?
Clean and scrub, scrub and clean. Some people recommend heating them in the oven or boiling them in water. I personally don't think either is needed. If you are worried about something possibly being in the rock you can soak them in a weak solution of bleach and water over night then rinse them, scrub them and rinse them again untill there is no detectible bleach smell left and then rinse them some more. I have had no problems with my rocks just scrubbing and rinsing them with a brush and hose. Do NOT use the power washers at the drive up car washes. There will always be chemical residue from the soaps and waxes left in the line. The best option is to get hold of a high preasure steam cleaner that uses only water.

Now your rocks are clean and your ready to build that perfect rock formation for your fish. Take a deep breath, sit down and think about it. Have a plan in mind before you start adding rock to your aquarium. The biggest rule here is to "LET GRAVITY BE YOUR GUIDE". Do NOT depend on silicone or hot glue to hold your stack together. It WILL eventually lose its adhession to the rock and will do nothing to hold things in place. If you must have that "special arch" use an aquarium safe epoxy putty to hold it together.

Lay out your rock out so you can easily spot that piece you may need. Practice making stacks on a table (cover it with cardboard if it's your spouses favorite.) Get a feel for how the rock stacks on itself and how high you can safely go. This is where the smaller rocks you collected come in real handy to fill in and help level your structure. Give it a nudge, press down on it and generaly give it the same jossle your fish might give it. Once you have mastered gravity and your structure can stand alone without slipping or falling you can begin using what you've learned about them in the aquarium.

Here we need to discuss the bottom of your tank. Some people prefer to put down eggcrate (light diffusers) to start their stack. This helps avoid scratching the bottom of your tank and supposedly helps spread the weight of the rock more evenly allthough their is some argument that it really doesn't help that much. Others just start stacking up from the bottom. It's all acceptable. Never, ever place your rock on a bed of sand. Your fish will will dig and undermine it with possible tragic results such as a rock slide or worst yet the fish becoming crushed under the weight of the shifting stone. If you are going to stack rock against the back of your aquarium keep in mind that most likely it will get scratched. In an older aquarium this isn't such a big deal as you will be putting your best veiwing glass forward.

I used 1 1/2" cement stepping stones available at any garden center to be the base for my formations. A chipping hammer will allow you to make them any size and shape you want and when you add your sand to fill in around them you avoid the dead pockets between the stones where noxious gasses may collect. Remember that fish like Mbuna prefer caves to hide out in and design your structures with this in mind. I also like to hide my filter inlets and outlets in the structure and place my heaters in there in such a way that they are hidden but still have a healthy flow of water going by.

In conclusion, have fun doing this. Take the family on a rock hunting picnic and allow the kids to do the heavy lifting on the promise they can place one stone in the aquarium. (Make sure you help them with this part.) This for me was a very easy and rewarding DIY project that the whole family enjoyed doing.
So put on your blue suede shoes and ROCK ON.

Great Article Norm!!!!

Good article Norm. I will be using the idea for the paving stones when I get my new rocks in later this month.

Good article!
I use a thick piece of dark plexiglass on the tank bottom to stack rocks on.

Great article!

Very nice article, Norm. I have one question for you about avoiding rocks with green deposits in them -- what are the green deposits composed of? I'm assuming it might be harmful to the fish?

Great article Norm.

If people will follow your advise, there will be a lot less headache later. I did learn the hard way by placing large rocks directly on the glass. Ruined two tanks that way. The bottom just split in halve. All it takes is a little piece of gravel under the rock and all the weight will concentrate on that point. This is what I do after I woke up:

ahh, the ole styrofoam in the tank trick... that's what I used to do also. That was the thing to do before people started using eggcrate (light diffusers). I remember mentioning that on a forum last year and a mod who had all of 6 months in the hobby acted like I was crazy for putting styrofoam inside the tank...

Nice diagram Klaus. Good to know there are still some "old school" hobbyists out there

I use the eggcrate as well.

Aura wrote:Very nice article, Norm. I have one question for you about avoiding rocks with green deposits in them -- what are the green deposits composed of? I'm assuming it might be harmful to the fish?

Generally if you have a rock that looks like it has green "powdered" throughout the stone more then likely it has a high copper content. You must also be very careful of any recently exposed rock that you find close to these copper rock. It only gets the green color when exposed to the elements and has weathered. When newly exposed it will have a rusty brown color and look a bit like the copper your used to seeing in plumbing shops.

http://www.caltelephone.com/lamps/copper%20world%20green%20rock.jpg

Copper in very weak solution does have medicinal benifets for certain fish ailments but constant exposure is deadly. When collecting rock if you have any doubt about it throw it out.

Klaus:
Yours is the first I've heard of stone preasure points breaking the glass. I will edit my article to reflect the dangers of stacking rock directly on the bottom.

This is a pretty good article. Emma and I went rock hunting a few times to get rocks for the 125g Cichlid tank. We have more than a 125g could ever hold but it was fun and we have some pretty cool rocks.

As for the kids doing the heavy work, I need to work on that cause I was the one wearing the back pack full of rocks and made multiple trips back to the car to unload. Oh, the pain!!!!!!!

When we aquired the 125g tank, the only place left to put it was behind a couch seperating a living room from a dining room so we do not have a "back". Also, to decrease some of the rock weight of the tank, we came up with some information on using concrete to make rocks for the tank. So, the tank consists of a bunch of light weight concrete rock and a bunch of real rocks. The rock forms were made using 1" styrofoam glued together in layers and then sculpted down to size and shape. We then hit them with a heat gun to remelt the little bits to keep them from shedding off.

For the concrete, we picked up a bag of fast setting "Patcher". There is a bunch of infomation out there about different crete mixes and what can happen to the water and all that. Let me say this, concrete mixes with high lime content will leach the lime and raise your pH. So, if you are going to use a crete mix to make some rocks, do some research and then do your own testing. Mix up a bit of the mix, make a ball, cure it, put it in a bucket of tap water and monitor pH for a few days/weeks. We had zero pH problems with the "patcher" during the new tank cycle.

Emma was pretty stoked about applying the crete mix to the foam molds. The rocks came out great. Emma coated everything except the bottoms. We then did a few float tests to make sure they had enough weight and had to scrape out some foam on a few and fill it in with concrete to add weight. The last thing you want is a rock that wants to float. Your fish will help it to the top and who knows what will happen to the rocks around it.

We weren't real sure how the rocks would look and how algea would take to them but by the time the tank completed the nitrate cycle, they were covered with algea and look like the rest ot the real rock in the tank.

We also have the entire bottom of the 125g covered with eggcrate.

Scott

I actually made lightweight concrete structures for my 350g project out of perlite, a little sand and type II cement. I was happy with the results for the most part and never have to worry about anything floating.
http://www.cichlid-forum.com/phpBB/viewtopic.php?t=156511&highlight=

Thanks for that info on the green, Norm. The reason I asked was my 75 gallon is piled full of rock that was labeled "green man rock" (I have no idea what that means.) I got it from a landscape supply and it's green, but not in the way you described or what's pictured in the link.

Sometimes a green rock is just a green rock.