Handling of an (unfindable) dead fish in a tank

Hi,

Anybody have any advice on how to succesfully break one of the most
fundamental rules in fishkeeping......?

I must assume that I have a dead adult (~10cm long) Pseudotropheus Acei in
my 240 litre Malawi aquarium. The fish looked decidedly off colour for a
day, and disappeared. The tank is quite heavily stocked (not initially,
but the way the critters breed (especially the Labidochromis) - and hide
(catching impossible)!) and filtered by a large 3 basket Eheim external
canister filter (~1000lph) and a 25W UV filter.

The tank has 2 remaining Pseudotropheus acei, uncountable Labidochromis
Ceruleus (5-6 adults, many juveniles), 4 Pseudotropheus Kingsizei, 4-5
adult and many juvenile Iodotropheous sprengerae and a pair of ancistrus.

In a nutshell I cannot find the missing fish. The entire back wall is built
up of stacked pumice and limestone which is glued in. Removing this wall
will necessitate a complete tank emptying and strip down. Suffice to say I
have poked a torch / hand into every accesible hole and moved every rock
that I dare. Short of emptying the tank, my options on finding the fish
are closed.

I have two options, the complete tank strip down, or to try and ride the
tank through the inevitable decomposition. I am hoping to manage the
latter.

My plan:

1. Reduced feeding, the fish will be fed once every three days instead of
daily.
2. Increased and forced oxygenation (airstone + extra eheim powerhead).
3. Daily 30% water changes.
4. Monitoring - I use anyhow an ammonia alert in the tank, and will start
doing daily nitrite and nitrate readings.

I am guessing that 2 weeks should be sufficient time for the fish to
completely decompose, and intend to follow the above regime for that time
(comments?).

The filter is due a clean (~1month since the last one), but since it is
still fast flowing I feel it best not to disturb its bacterial population
whilst the biological load will be rising.

Any advice welcomed, especially from someone who has practical experience of
managing something like this. Am I worrying too much, or not enough?

Cheers,

Gary Whitehead.