What do we put underneath large rocks in Aquarium?

[sweetpoison]

So I was watching a YouTube video but it was not in English and it looks like he put big square pieces of Styrofoam underneath his big rocks Instead of directly on the tank floor. Can you put Styrofoam in water?

[Guppysnail]

Use egg crate. It’s plastic grid for light covers at hardware stores cut it to size to disperse weight

[Widgets]

High porosity sponge would also work. But, if you are using a UGF for the tank, it would serve as the pressure relief plate.

[nabokovfan87]

Lots and lots of sand.

I wasn't a fan of the light diffuser because the material is extremely sharp and fragile. I had a lot of concerns with it shifting and cutting out the silicone, even if I sanded it. The material is just really stiff and very sharp if anything snaps a piece off.

[Patrick_G]

I generally put rocks on top of the substrate, but the one time I needed to put a rock on glass I used piece of close cell foam. 

[Ken]

I use something called plastic canvas. All the craft stores have it. Super cheap and makes a good light light diffuser too.

[OnlyGenusCaps]

So, I always put rocks right on the glass.  Carefully.  But I've done this for years with 20+# rocks with no problem.  I do this for two reasons:

1) Aesthetics - rocks look more natural when they emerge from the substrate.  Putting them on top of a layer first often makes them look odd to me.  This is true for the light diffuser as well.  Plus, if you have diggers, they can uncover it and that's just ugly too.

2) Stability - back to those diggers, if you have digging species of fish or snail and fairly extensive rockwork, I have been told (please note, I do not have first hand experience with this - nearest is a friend with a SW tank there this happened) that the digging can cause the rockwork to be come unstable and it can tumble.  Sometimes even scratching or breaking the glass.  Plus there is the smaller scale danger of crushing your inhabitants. 

To avoid both of these issues, I always create a stable structure first (at least with the first layer), and then backfill with substrate.  That said, I am intrigued by @Ken's idea of using the "plastic canvas".  It is so thin that I don't think you are likely to run into any of the issues I've raised.  I've just never heard of anyone using it before.  This might be a game changing innovation for me!  Thanks, Ken!

[sweetpoison]

On 4/10/2022 at 4:45 AM, OnlyGenusCaps said:

So, I always put rocks right on the glass.  Carefully.  But I've done this for years with 20+# rocks with no problem.  I do this for two reasons:

1) Aesthetics - rocks look more natural when they emerge from the substrate.  Putting them on top of a layer first often makes them look odd to me.  This is true for the light diffuser as well.  Plus, if you have diggers, they can uncover it and that's just ugly too.

2) Stability - back to those diggers, if you have digging species of fish or snail and fairly extensive rockwork, I have been told (please note, I do not have first hand experience with this - nearest is a friend with a SW tank there this happened) that the digging can cause the rockwork to be come unstable and it can tumble.  Sometimes even scratching or breaking the glass.  Plus there is the smaller scale danger of crushing your inhabitants. 

To avoid both of these issues, I always create a stable structure first (at least with the first layer), and then backfill with substrate.  That said, I am intrigued by @Ken's idea of using the "plastic canvas".  It is so thin that I don't think you are likely to run into any of the issues I've raised.  I've just never heard of anyone using it before.  This might be a game changing innovation for me!  Thanks, Ken!

Very informative thank you so much!  I have always put everything directly on the substrate or the tank bottom as well.  I’ve just been watching some YouTube videos and that is not what they do so I started trippin🤭😂

On 4/8/2022 at 6:18 PM, Widgets said:

High porosity sponge would also work. But, if you are using a UGF for the tank, it would serve as the pressure relief plate.

Ok Widget ~ UGF?  Is that Mike a light or something?

[AndreaW]

On 4/11/2022 at 9:18 AM, sweetpoison said:

UGF?  Is that Mike a light or something?

UGF - UnderGravel Filter.

I have an UGF in my 46G so that helps distribute the weight and would keep anything with a point from putting pressure directly on the tempered glass bottom. I also secured my large, heavy driftwood to rocks to give it a stable base so I don't have to worry about things getting shifted, unbalanced, and possibly tipping and hitting the glass at the back of the tank.

I pushed (wiggled and shimmied) the driftwood/rocks down into the substrate so it looks more natural and "settled" and added some extra rocks around the base as well. 

[R Budds]

On 4/8/2022 at 8:45 PM, sweetpoison said:

Can you put Styrofoam in water?

Yes. Some people use foam board insulation (the thick foam used in house construction, it comes in various thicknesses) for backgrounds and fake rocks. Also Greatstuff can be used, it's in a can and expands when you spray it; it's good for locking rocks together. 

I use EPP foam. It's the soft stuff that computers are packed in,  but I buy the sheets from model airplane suppliers. I use it for surface dividers for duckweed, I cut it a little long and bend it a little to put it across the top, this way it holds itself in place. 

Here is one in my 20 gallon. I slide it one way or the other to push that section of duckweed together and scoop it out, then slide it back.

I don't know of anyone else using EPP, so use at your own discretion. 

The main things are that it's a closed cell foam (that won't absorb water) and that's its free of contamination.

Edited April 11, 2022 by R Budds

[Widgets]

@AndreaW makes a good point. If you have hardscape that is perched in such a way that it could topple if disturbed by you or the tank inhabitants, you need to secure it for the safety of your tank, it's inhabitants, and the area around the tank.

[Brian]

I use Under Gravel Filters.  Large rocks/decorations are not a problem.