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QUESTION: Would glazed tiles be safe on the floor of an aquarium for discus fish? 19/01/09   West Bengal, India

I came upon yr site on the web.

I am establishing an aquarium and will like to use newer glazed tiling which replicates natural stone in grey or brown for the floor of the aquarium. The fish are discus which are quite sensitive to water conditions. Can u kindly let me know whether there will be leaching of lead/metals in amounts which could be harmful to the fish. I read somewhere that as floor tiling needs to have high abrasion resistance they are fired at high temperatures  which negates the leaching of metals. I realise that this request is somewhat personal in nature but any opinion that u can offer will be deeply appreciated.

Many thanks


Sent: Friday, February 20, 2009 7:00 PM

 Dear Elizabeth,

Thanks so much for the response. deeply appreciated.


ANSWER: February 20 2009

Dear Anil,

I knew nothing about aquarium conditions for discus fish so I found the article at which states:

"Here is what the recommended pH is:

  a.. Display - 6.0 - 7.5

  b.. Breeding - 5.5 - 6.5

  c.. Growing On - 6.5 - 7.5"


"Below are the recommended temperatures for Discus Fish tanks:

  a.. Display - 27.5C to 29C

  b.. Breeding - 30C to 33C

  c.. Growing On - 29C to 31C"

 Since you are asking about the potential of lead leaching from glazed tiles into the aquarium water, these pH and temperature ranges are concerning. The more acidic the water and the higher the temperature, the more lead leaches from ceramic glazes, though as you point out, high temperature firing lowers the potential for leaching. The other factor that raises the rate of leaching is cracking or chalking of the glaze, which can occur variously during firing or in response to sunlight or harsh chemicals or over time. All in all, I am not convinced that leaded ceramic glazed tiles are a good idea in a fish tank but when you consider that they will need to be adhered and grouted (and that both adhesives and grouts have been known to contain lead and are certainly not non-toxic), it really seems to me to be worth considering more natural alternatives such as stones or gravel. I hope this helps. It would be useful to me to hear back from you as to what you decide to do.

Yours Sincerely

Elizabeth O'Brien

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