Fantastic, thanks for all your help. I think I'm pretty sorted in my mind abot what I want to do now then. When my tank cycles I have been told that I can stock it quite fully immediately. Is this true? I don't want to overload things or harm my first fish. How would it be if I put in 4 or 5 platys, 6 cherry barb and six corys.
I realise that under normal circumstances this would be a huge load on the filter but, unless I have misunderstood something badly I think the cycled tank would be able to cope.
Am I right or way off the mark?
Glad to help

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As far as i am aware you can stock a tank which has been fishless cycled entirely if you want, but personally i would not buy all the fish at once as more than often, fish bought at petshops are often carrying one desease of one sort or another and may infect all of your new fish once in your tank. So i would buy a large percentage on the fish you are planning on getting, but not all of them just yet in case you encounter any deseases or parasites amoungst the fish and have to treat them. After you've bought your first lot of fish, i would let them settle in for a couple of weeks at the least so they can adjust to the new tank and also so you can easily spot any problems that may arise amoungst them

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If the tank in the shop you are buying your fish from has unhealthy ones, i would avoid buying any fish from it as some parasites and deseases on fish can be particularly infectious and may also not show the symptoms of the desease or parasite imediately (like whitespot).
Check fish in the petshop for things like;
a. If they are underweight/skinny looking at all
b. Have inflamed anus or white/string poop
c. Hanging around the bottom or top of the tank a lot when they shouldn't be
d. Gasping or rapid breathing
e. Flicking or rubbing themselves on objects in the tank
f. Cottony or slimey looking infections or growths on the fish or general discolouration
g. Spots like white sand grain sized spots on the fish or dusting of fine gold like spots on fish etc.
h. Tattered looking or ripped fins/fins with chunks missing out of them
i. Swimming about like they have lost their balance like swimming around in spirals
j. Bent spine or warped looking flesh
k. Suspicious patchs of discolouration on fish
l. Missing scales or scales sticking out
m. Blood like markings under the skin
n. Cloudy looking eyes or eyes popping out
o. Bloated apperance
p. Fish generally not very active for its type/looks under the weather
Etc etc...There are many things you should look out for when buying new fish. Also, i would also ask the staff at the shop how long the fish you are intending on buying have been there for- if they only arrived that day, i would avoid buying them for a day or so as many fish in petshops are made to endure many hours or even days of more or less being constantly transported from one place to another and so are very stressed/unsettled and hungry by the time they end up in the petshop.
Letting them settle into the petshops tanks for a day or more will help improve the chances of you successfully acclimatising the fish to your tank. If you are concerned the fish you want could be sold during the time you are waiting for them to settle into the petshops tanks, you can ask if the staff put your fish aside/keep your fish for a couple of days first before you buy them (most petshops will more than happily do this for you)

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Edit: Have you got any food for the fish you are going to get yet? A varied diet is best for fish, fish flakes or pelets aren't nesarsarily good for all fish.
I always find it also helps to have a couple of meds in stock too even if you have no sick fish, sometimes problems can arise with fish through no fault of your own and it always helps if you can treat any problems that arise with them as soon as posible

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