Since it was requested here is a guide on how to build Slate Caves for your plecos.
First of all you need the following tools/materials in order to make the caves:
1.Dremmel Cutting Tool
2.Nesccesary Slate plates
3.Diamond Cutting Discs for Dremmel
4.Hammer (preferably a small one)
5.Silicone Pistol
Here you can see several Slate pieces.Try to 'imagine' which will be the best piece for your caves!
Here you can see the Dremmel along with the Diamond cutting Discs.

Here you can see the disc fitted on the Dremmel.Don't try to cut Slate with any other type of Disc as it wont work because of the Slate's composition.Diamond Discs are the best for the job.

Here you can see the hammer that i use.Try to find a small hammer with a 'thin' side as the one pictured in order to 'remove' smaller peices of slate.

This is the Silicone that i am using.Ofcourse it is 100% pure Silicone which is suitable for aquarium use.

In order to cut the necessary straight pieces for the two sides and the back of the Cave i always start with a straight piece of slate.

The dimensions of the pieces depends of the size of your fish and i personaly make my caves in different size almost every time,judging by my fish.Here are the three needed pieces.

Now choose the bottom piece.Try to 'imagine' how the cave will look like when finished and select the best piece.

Now,after you selected the desired piece with the hammer hit gently the edges in order to shape them to look more naturely.
Here you can see two bottom pieces rounded.


Now it is the time that you have to glue with silicone the side and back pieces to the bottom of the cave.
First apply a thin layer of silicone to one of the side slate pieces and gently place it on the bottom piece.With the same way attach the other to pieces.
Here you can see the results...



Then you have to wait 30 minutes (depends of thr silicone used) until the silicone sticks.
Now you have to find/cut the top Slate piece.As it was described before try to change the shape of the Slate with the hammer or with Dremmel (if you prefer straight shape).
Here you can see the top pieces and the other parts of the cave.

Now apply a thin layer of silicone to the top of the side and back pieces.Place the top piece on top of the other other half of the cave and accordingly wait 30 minutes for the silicone till it sticks.
Then you have a beautifull cave for your fish!Simple as possible!
Here it is!


I personally never had a problem with the caves,never had an injured fish and of course they are 100% safe to use!
I wish you a lot of spawns and i hope i helped on this!
