Mat under large Rocks

[peter]

I am building a new freshwater planted aquarium (48x24x24) that will have a large group of heavy rocks (black slate with lines of white quartz) at one end. I think that I should put something on the bottom before placing the rocks, to prevent scratching the glass base of the tank and to spread the weight of the rocks.

What material should I use for this "under the rocks" mat?

I thought about using a rubber car floor mat but I worry about the rubber breaking down underwater. In any case, rubber mats smell, indicating that chemicals are slowing coming out of the material.

I thought about non-slip bathroom floor mats, soaked for a few days to remove any anti-fungal chemicals, but I don't know what they are made from.

I thought about thick scuba-divers wetsuit neoprene rubber but I worry that it'll compact and transmit the weight pressure to the glass.

I thought about using under-gravel filter tiles but I don't know if they'll crack under the weight.

Any suggestions and ideas?

Regards
Peter

[William]

I would use frigolit (is that the correct english name?)

[peter]

I would use frigolit (is that the correct english name?)William,

Do you mean styrofoam - the white stuff that they pack around computers and TVs?

Is it chemically inert?

Regards
Peter

[William]

Yes. I mean styrofoam.

styrofoam is supposed to be aquarium save and never had any problems while using it. It is widely used when making aquarium background and to protect the bottom glas.

[NorthernBoy]

yes use styrofoam...you can buy like 1/8 in sheets at the post office for pennies. You can also use silicon on the rocks to adhere them together so the don't tumble over and crack your aquarium.

[peter]

As you can see from my profile, I live in Bangkok Thailand. Things are not always done the same way here as in the West. Two local planted aquarium experts told me to just put about 2 to 3 cm (1 inch) of gravel and then place the rock onto the gravel. They reckon that the gravel will work its way into the shape of the bottom of the rocks and spread the load over the glass. Then the rest of the substrate (about a total of 8 to 10cm (3 to 4 inches) deep) can be placed around the base of the rocks to help hold them in place.

Has anyone had any bad experiences with this kind of approach?

Regards
Peter

[NorthernBoy]

depends...do you care if 120 gallons of water crash to your floor and stink like fish poop and rotting fish food? If not don't use styrofoam!

[William]

Don't use gravel between the glas and large rocks. The gravel can concentrate the pressure to one point (if you have bad luck) and the aquarium brakes. Having gravel under large rocks can also be a problem if you keep digging fish.