Aquascaping

The scenery in aquariums varies from nearly empty tanks to a solid wall of rock. Once it's in place it's hard to change so it's worth planning it out. A creative aquascape can really bring an aquarium to life. Here are some tips I found useful...

stability - no matter how good it looks it's no good if rocks fall over - the fall could kill your livestock or even damage the tank. They should be secure enough so that they stay in place when knocked gently by you. It's surprising how easily a sudden surge of water or a large turbo snail can cause a rock to slip

water movement -

corals and some fish have individual flow requirements - too much or too little and the coral will die.
to get the best filtration out of the rock there must be good flow around them. Try to leave as many gaps around the rocks as possible.
Good water flow also prevents detritus from settling and causing algae outbreaks.

Sketch of our tank layout. Grey is the rocks, blue the water outlets. The inner shapes represent suspended rocks.

livestock - most creatures will appreciate places to hide and some fish require more open swimming space than others. Try to think ahead - if you plan on keeping Tangs then they won't appreciate a tank stuffed full of rock. Equally Angels will feel less secure in tank with one or two rocks and no hiding places - they like to weave in and out of rockwork. If you plan to keep corals think about light too. Make sure you don't create too much shade when you aquascape. It's worth checking as you go that you haven't created an area when that's too dark for most corals. Of course some creatures like shade - eg sponges - and others - eg mushrooms - will generally tolerate lower light levels.

appearance - personal taste but it helps to think of formations that occur in nature - overhangs, channels and spurs. In an aquarium it's all in minature but one or more of these can usually be worked into a tank. Imagine your ideal scenery; sometimes it helps to sketch it out. Next, before you actually place the rocks work out how you are going to construct it. The obvious way is to pile smaller rocks onto larger ones. This can look good but cable ties and pipe gives you more options - details below.

methods of constuction

the base layer - some debate on the best way to do this but whichever way you choose, if its supporting rocks above it needs to be very stable. Options for placing the base layer:

on eggcrate or glass shelving that has been secured to the tank or is itself a solid independent structure. Tricky but would allow water flow and you can use less rock.
directly on the glass base - some claim this can damage the glass but I've not found this to be so.
on short vertical sections of pipe - personally I think it's hard to achieve real stability with this method
on a thin layer of sand - this is what I did. Push the rock into the sand till it mostly touches the glass - kind of like bedding in paving. Rocks are never even so this helps stabilise them. There should not be enough sand under the rock that might allow a creature to end up crushing itself by digging out the sand - or even cause a rockfall.

Once you have the base layer it then depends on your plan as to how much rock goes on top.

cable ties and pvc pipe - I first saw this idea in MCRA vol 1 and experimented a bit. With the pile 'em high method you will often find that as you build higher the rocks become less stable and you have to use smaller and smaller pieces - difficult not to end up with a wall or a cone shape. A wall or cone construction can give you more "shelf space"for corals but if you want something different try this:

Fish like these need open swimming space to thrive

This T-shape section is actually three rocks held together by ties and suspended from PVC pipe.

Top view of the same section showing the ties and pipe

Get some cable ties - generally used by network installers and electricians. It's useful to have a selection of lengths. Also they can be tied together for longer lengths. The mechanism on these ties is very strong as are the ties themselves.
Drill holes in the rock you want to suspend or join. Place the rock on a firm surface well away from the tank. If its reef type rock an ordinary masonry drill bit goes through it quite easily. Reef rock is quite soft and will be damp so you will probably need to clean the drill bit a few times. Make sure the hole is not too near the edge of the rock - reef rock can break. Also don't rely on just one hole and tie - especially if you are suspending. If you are joining rocks then drill both pieces, thread the ties through the holes and then close up the ties
To suspend rocks you can thread them over a centre brace if you have one or over pvc pipe. Rocks are heavy when wet so use the strongest pipe you can get - ideally rigid. ABS is good to.
Decide where you want the rock to hang then measure the length needed to traverse the tank at that point - usually back to front of the tank but you can lay the pipe diagonally or in the corner
Cut pipe to length and then half cut both ends - this is to stop the pipe rolling. The two cuts need to be parallel otherwise the pipe may rock a bit.

Viewed from the side it should look something like this

Put the pipe in place by resting it on the sills and check it's in the right place and stable.
hold the rock below the pipe and decide where to put the holes.
drill the rock and thread the ties through.
Hold the rock below the pipe and close the ties over the pipe. Don't fully close up the ties - do that when you are happy with the height of the rock

cable ties - cheap, tough and widely available

close up of a half-cut end resting on the corner of a sill