Gex or Sudo sand for bichir substrate?

[Kinokunya]

Hi people,



I'm planning to do a rockscape similar to the above for my bichir tank. I'll be needing at least 5cm depth of substrate so that the rocks don't fall off from place. Did some reading off the net and found out that thick, compacted substrates might give rise to the toxic Hydrogen sulfide (H2S).

Quoted from other source:
Large particle substrates allow more uneaten food and waste to penetrate into it leading to toxic build ups if not cleaned. Small particle substrates can compact which may lead to areas that lack oxygen. These areas can eventually release hydrogen sulfide – a substance that is extremely toxic to fish.

Would it be advisable to use black fine sand as shown in the picture below.


Alternative would be the hefty 8kg bag of Gex soil for my tank.


Am thinking of driving deep down some dwarf hairgrasses (Eleocharis parvula) despite the known fact that bichirs are bottom dwellers.

Thank you.

[barmby]

I will choose sand over soil because soil will create murky water when stir. This is quite personal. No right or wrong. However, soil is very fertile and grow grass everywhere