Stone recommendations for Malawi tank

Hi guys.

Benn a while since I posted here. My tank has been closed down for over 2 months due to starting a new job and moving from London to Birmingham.

I have started setting it back up this weekend and have decided that I will have a Malawi Cichlid tank. This is mainly due to the water where I live is best suited for them, and my son fell in love with the yellow labs at my LFS.

I spent yesterday cleaning the tank before doing a few coats of black paint on the back, I had hammerite left over from painting the patio set last weekend, I’d never advise anyone to do the same. Although it worked after a few coats with a sponge roller, metal paint does not like glass.

I have washed a bag of kids play sand for the substrate, I have left it rough on the bottom as I like the look more than when the substrate is flat and smooth.

My main question now is what rocks to use to make a nice feature in the tank that I can build caves and hidey holes with for the fish.

I have a trigon 190 corner tank, I would like to start the stones/rocks off lower at the front and build them up higher as I work towards the back of the tank.

I have seen some people using ocean rock, this provides plenty of hiding spaces for the fish but gives the tank more of a marine look.

I was thinking of buying a couple of the blue/black natural limestone slabs from B&Q and breaking them up, would this work?

Thanks for any help

Limestone and sandstone are the rocks normally used for rift lake and marine tanks. They are calcium based and help keep the pH alkaline.

They are quite soft and easy to work with so if you have a wood rasp for shaping wood, you can use that on limestone to shape the rock. And you can drill holes in it with a masonry drill bit. You can also put vinegar on limestone or sandstone and over time it will dissolve the stone and leaves a hole behind. You usually have to keep adding acid over time as it becomes neutralised by the limestone. We used vinegar on big round bits of limestone to make tubes for fish to hide in.

Limestone and sandstone are both cream/ white in colour. If the rocks are black, brown or blue they are not limestone or sandstone.

You can use river rocks but they won't help with keeping the pH alkaline.

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A can of spray paint works well on glass. Just make sure the paint dried completely before setting it up.

The hammerite paint worked, it was just hard work lol.

As for the black limestone, limestone can come in a variety of colours. I’ve seen black, brown, green and obviously cream. Not sure if the mineral content is different for each though.

I had already been and brought the slabs before I saw your reply and broken them up. Hopefully they will be ok. I am in the process off putting some pieces together and will leave them in the tank for a few weeks while it cycles, i will test the water every couple of days for ph and hardness to see if it buffers the water too much.

The piece I have put together so far is pretty sturdy but I’m always nervous with Fish banging into stones in a glass tank. I have some black aquarium safe silicone, would this work for bonding the stones together more? Or should I hold off and buy some stone cement?

The photo below shows one side ready to be smoothed down, cleaned and stuck together

is the grey rock in the picture the limestone?
It looks like slate to me. Slate is safe and limestone is safe. But if that is man made limestone that has been dyed, then it could be an issue.
They make limestone bricks and blocks by squishing and gluing crushed limestone together into a block. They don't normally stain or dye it here but other countries might.

Slate is hard to drill into but limestone is easy so try drilling a hole in the rock and see what happens.

You can drill holes in the rock and use pvc pipe as dowels to hold the rock together. Then you can assemble and dissemble the rocks as required.

That does look like slate - in which case its perfectly safe and won't affect your water. If it is limestone it also contains something else to create the colour (man made or not), which may leach out and prove harmful.

It is natural so hopefully no additives, I’ve taken a few photos to help me remember how it goes together. Going to smooth the edges down now with a file then soak it all in boiling water for a while.

I’ll leave it to dry overnight and stick it together in the morning, will have to do it in a few pieces to make it easier to move and place in the tank.

Fingers crossed it all goes well

This is my final design, it measures 55cm in length on both sides and 45cm tall at the middle

I'm not sure if you planned to or not but try to attach the rocks with some sort of aquarium safe sealant, those rocks are quite big and should stay in place because of the weight but you just never know with cichlids. My labs are psychos sometimes and will collapse caves. Other than that, those look awesome, I am a big fan of that type of setup.

Yeah I used aquarium safe silicone. Due to the size of it though I’ve had to build most of it in place in the tank.

Going to let it dry for a couple of days before adding the water, hopefully it will be solid by then.

I’ll get a picture in a minute of it when I put the light back on. 1:30am and I just finished piecing it together again

Make sure there is a decent gap between the glass and rocks so fish can't get caught between a rock and a hard place. Fish sometimes try to go through gaps between ornaments and the glass, and they don't always make it. Alternatively make sure the rocks are touching the glass so the fish can't even see a gap to try and go through.

You also need to be able to remove the gunk that will collect behind it.

I’ve left about 4-5cm behind most of it so they should have enough room.

Never noticed how scratched my tank was till I took that photo, it looks awful

I'm using Pebbles