# Background



## Marvin (4 mo ago)

Hi there.

Excuse me for my terrible English.

I'm trying to build a background I have some stones and secured then with expanding foam. I'm from the netherlands and we only have yellow expanding foam. I saw some black ones but they were pretty expensive. I want to use concrete or grout to conseal the yellow expanding foam. Now I'm doing research and almost every website says something different. Is concrete or cement save to use. Is grout a better solution. I heard somewhere that tile glue is good too but also not. Can't really get any answers on dutch forums maybe you guys can help me out?


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## characinfan (Dec 24, 2008)

Hello there! Your English is fine.

I would not use foam or expanding foam in an aquarium, or concrete or cement. All of these things will negatively affect the water chemistry. If you want to build a background out of slate, use aquarium-grade silicone. There are videos that show how to do it.

Good luck!


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## kharmaguru (Jan 6, 2013)

Marvin said:


> Hi there.
> 
> Excuse me for my terrible English.
> 
> I'm trying to build a background I have some stones and secured then with expanding foam. I'm from the netherlands and we only have yellow expanding foam. I saw some black ones but they were pretty expensive. I want to use concrete or grout to conseal the yellow expanding foam. Now I'm doing research and almost every website says something different. Is concrete or cement save to use. Is grout a better solution. I heard somewhere that tile glue is good too but also not. Can't really get any answers on dutch forums maybe you guys can help me out?


If the object is to cover the yellow foam, this product will also seal it and is aquarium safe once cured - Plastidip










If you have concerns there is also this product that is made specifically for ponds and will also seal the foam - Pond Shield.










Perhaps the same or similar products are available in the Netherlands. Hope this helps.


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