This last piece of information has left me stunned. Few British aquarists now use undergravels at all and those that do use them on smaller 2' long aquaria - not larger ones. On those they invariably use external filters - not hang-ons but canister filters set inside the cabinet. These have almost endless advantages over undergravel filters, and few disadvantages. I live in hope that an American reader of this page will (quickly) put me straight on this.
There's no doubt that undergravels are an efficient means of filtration but (unless used in reverse-flow mode) they trap vast amounts of waste, need constant attention, and invariably begin to clog in areas away from the main water flow (produced by air pump or powerhead) and are poor for plant growth. As you'll have gathered, I don't like them - but I have a few correspondents who radically disagree.
As for hang-on filters they seem to me to be an excellent idea on a smaller tank and I can't understand why they haven't caught on more in this country. Easy access for maintenance, and greater adaptability than other small filters (which go inside the tank) are two huge points in their favour. When I have used them I've really liked them.
Another problem with the book has been the recommendation for beginners not to keep guppies and Cardinal tetras. I don't like guppies because they have inbred disease problems, flowing fins that get ripped and pulled to pieces, and the males are serial rapists meaning that any imbalance in the gender ratio may cause problems - and if you don't have an imbalance they quickly breed and produce one...
Cardinals are so often confused with Neons by beginners - and actually I'm not keen on Neons either as they too seem to have inbred problems. Cardinals really do need acid water to do well and in the UK at least that isn't always easy to get from the tap. I think beginners should be able to use tapwater.
I've also been picked up on some daft little errors which deserve to be pointed out (talking about low readings of pollutants but mixing them with low pH as though that's a problem) but what this serves to prove to me yet again is that one man's fish is another man's poison. It's dangerous to be thought of or try to be an "expert" in fishkeeping - because there's more than one way of achieving the healthy care of any fish.
© Steve Windsor. May not be reproduced in part, or whole, without permission.