Thusly "NetMax" Spake Unto All:

peroxide could help with the smell. I presume you know about devices
like this?:
http://www.malawicichlidhomepage.com.../oxydator.html

No I wasn't. Interesting device. The odour is not too strong. I don't
notice it in the shower, only when I'm using raw well water, and even
then it's not strong, just enough to cause some concern for the fish when
I get up to 20% water changes.

The human nose can detect hydrogen sulphide at extremely low levels;
the material safety factsheet suggests down to ppb concentrations,
whereas toxicity to fish is cited in the ppm range. Your fish are
probably quite safe.

As for oxydator/oxidator, I've tried a home-made variant (a 0.5L pet
bottle with a pinhole in the cork, filled with 3% peroxide and turned
upside down in the aquarium; the oxygen gas produced by the
decomposition of the peroxide pressed out about 10ml of peroxide per
day though the pinhole), and it DOES increase the ORP, does oxidize
organic compounds in the water, and does seem to make algae miserable,
but my home-made contraption released too much peroxide which made the
fishes start scratching themselves, and killed off some plants. I'm
still quite interested in getting hold of one of the commercial
devices, though.

WRT hydrogen sulphide, peroxide should work like ozone, and reduce it
to non-toxic & odorless sulphate (AFAIK).

If you can, email me

Details are in the mail.