I wonder if anyone has used a Trident Topflow Biological Filter. The
filters are made in the UK, and are made of the box type design
consisting of three layers of foam mat and some Flocor medium below.

The Company issues what it calls a 'Clear Water Guaratee'although it
does not state what if anything it will do to recompense a purchaser
who finds the filter as useless as it in fact functions.

I purchased and installed two 12000 litre filters to filter my 2000
gallon koi pool, within days the pool became and still remains like a
sewage works sludge tank. One of the problems is that the matting fits
the tank until the tank is filled with water whereupon the tank
distorts in shape and leaves a one inch gap between the filter wall
and matting. Water therefore bypasses the matting.

The company insists this should not cause a problem and are trying to
convince me that despite the matts the water will preferentially flow
through the mat!! IE water prefers to flow through the route of
highest resistance.

I have emailed the Company to complain and was met with a tyrade of
arrogant abuse. The Company states they can produce a lot of letters
from satisfied customers, and yet when I ask them to do so they have
refused to make these available.

Please, please please anyone thinking of buying this type of filter
please think again, learn from my expensive experience, get a proper
Koi Filter system and do not waste your money of these filters which
basically are sold and constructed by confidence tricksters.