should we move on

I cycled my older Tank in 8 days, getting a squeeze from my lfs filter medium, left it with 3 fish in for a week and hey presto done, so why are Forums telling everyone to do a fishless cycle that takes weeks or even months, my question is, should we move on

From a retailer's perspective...
we need to give advice, that when followed, works.
To give an example, the answer to the question, "Will a Siamese fighter be OK with my guppies?", is always, "No, the fighter is likely to attack the guppies". The nuanced answer is, "There's about a 60-70% chance that the fighter will attack your guppies, whether it does or not depends on, the size of your tank, the colour of your guppies, the colour of the fighter, the number of guppies present, the amount of plants & other cover available, the temperement of both the guppies and the fighter and what other fish are present in the set up."
Unfortunately if I give the customer the nuanced answer, in many cases they hear what they want to hear, namely, "Yes", and then come back and complain to one of my colleagues that the fighter I sold them has attacked their guppies and I told them it would be, "OK".

When it comes to maturing a tank, we retailers have to balance the expectations of the neophyte fishkeeper, ie that they can take the fish & the tank home together, fill it with tap water and have a dozen goldfish swimming around in a 15 litre biOrb by teatime; with the attitude of some residents of some of the forums who feel that a 180 litre tank needs to be matured for 2 months before any fish are added, that at best it's suitable to house 6 neon tetras and three cory cats, and that anyone who doesn't test their aquarium water twice daily is being negligent!

In practice the truth lies somewhere between these two extremes, and really calls for a nuanced answer which won't go down well in some quarters....

IMO

It's best to mature the tank before the addition of fish, this can be achieved by the addition of Plants & Tetra SafeStart or better still by the addition of mature filter media from from a mature tank. Despite doing this you may see a rise in ammonia and/or nitrite and you may still find that the tank takes weeks or even months to fully mature, equally you may find your tank is more or less instantly mature.

Whilst it's true that that high levels of ammonia and/or nitrite are damaging to fish, in my experience there are many species who seem tolerant of, and suffer no long term harm as a result of, short term exposure to low to moderate levels of these chemicals.

The problem is that it's very difficult to predict exactly what levels of ammonia & nitrite will be seen in any given situation.
For example, we recently converted some of our marine tanks to freshwater. Since our tanks use undergravel filters we were able to pinch gravel from other mature tanks to seed the new filters, despite doing this, stocking lightly and re-seeding two or three times, whilst some of the tanks matured quickly others took weeks and showed persistent, and surprisingly high levels, of both ammonia & nitrite.

In general, lightly stocked, lightly fed, large tanks run by experienced aquarists seem to mature very quickly. Conversely small, heavily stocked and over fed tanks owned by inexperienced fishkeepers can take months to fully mature.

In practice it's easiest to give a "blanket" answer, "add plants & safestart/mature filter media, leave for two to three weeks, if by that time you've not seen any sign of ammonia & or nitrite, you're safe to slowly start adding fish. If there is any reading of ammonia or nitrite, don't add any fish until both readings are down to zero, this process usually takes between 2 and 6 weeks, but in some cases can take as long as 3 months. Patience is a virtue!"

I can see your point being a breeder and a shop owner Rob, you do have to give the best advice, a lot don't, I admire you as a trusted Aquarist,
it's when I read people taking over a month to do a fishless cycle it galls me, when it could be done with (proper water tests) a lot sooner, most LFS will give a bag of media, I just think the fishless is so laborious..........

I've just finished setting up my old Juwel Rekord 800 for my angel fish pair to live in alone and I was worried about getting the filter going.
Once I had the tank back in the house I took the filter sponges and chucked them into a bucket. Then I emptied one of my two external filters from my main tank (rio 240) and tipped all the water and gunk from the canister into the bucket with the 800's sponges. Then I gave the 240 a tidy round and removed any dying leaves from the plants. Anything that was decomposing went into that bucket aswell and finally I added an air stone and left it for about 3 days.
Once I was ready to fill the 800 with water I added the sponges to the filter and tipped the thick of the gunk from the bucket over the top. I put a net in and all the dying leaves went in there and for 2 days I was chucking in large pinches of flake too. The whole thing stank!
Yesterday morning I decided to bite the bullet, be brave and move the two angels into their new home. I dropped 50% of the water out of the 800 and replaced it with water from my 240. Then I robbed the other external filter of two handfuls of ceramics and a fine filter wool pad that was thick with brown slime. I crammed all that into the 800's filter and put the angels in.

I've worried all night about them and the first thing I did this morning was an ammonia and nitrite test. I honestly expected to find something but both tests were zero.
It would seem I'm looking at an instantly cycled tank and no fishless cycle was needed! As Brian has said, it seems to be possible to cycle a tank instantly with a squeeze of gunk from another filter.

I'll still carry on testing for ammonia and nitrite for at least a week and I'll only be feeding very lightly aswell just to be doubly sure it's cycling and no harm is coming to my precious angelfish pair