Number Of Females To A Male

[KittyKat]

* 6-10+ Corydoras of one species - I had 2 in my small 31 litre (as recommended at the time by my LFS due to tank size) - once I get a bigger tank these will be moved out of this tank

My experience is very different from what your LFS recommended: if there are enough per species to form schools, the different Cory species will not even mix together. It is pretty much a solid fact that all Corys are schooling or shoaling species… fish are aware of others of their own species in a "me", "me + one", "me + two", "me + three", …, "me + few many", …, "me + many many" sort of way. In my experience, 5 fish in total is "me + four", 6 fish is "me + few many" and "me + many many" is usually 10-15 (varies between species). For some species, those barriers are at even higher number, but I do not know of any species where they are lower. Shoaling (including schooling) species (I say) must be kept in groups because it is a self-defence mechanism and the behaviour that they exhibit when not in groups is very odd compared to "normal" behaviour.

* 10+ harlequin tetra (what is this species? I have never heard of it before… sure it is not a rasbora? If it is the rasbora, then make sure to get only one species out of the three) - harlequin tetra is what I was told when I brought them, again when I had the small tank and didnt know any better - these are going to a friends tank in the near future as they brought 4 at the same time as me

Any chance of a photo? It would be nice to get an ID for the common name.

* 5 guppys (2+ females per male or all of one sex, and really, these shouldn't be in here because of water requirements) why shouldnt they be in ? my water stats are perfect, you have lost me and believe me I will be bollocking my LFS if I have been given bad advice AGAIN - also 3 females, 2 males is what I have
* 3 platys (1m 2f or all of one sex), and these do not mix well with the others due to water requirements, again why not ? brought these with the guppys and were told it would be fine

They are hard water fish and do not do well in soft water in the longer term, but most of the other fish you have are soft water fish and are more susceptible to problems if kept in hard water. They might be "fine" for a month, a year, but they will not be fine in two years, five years, and this will show in their health. If you ask your LFS, they are quite likely to tell you that water hardness does not matter… but I recommend that you do a crash course on osmoregulation, effect of pH on bacteria/fungi and development of livebearer fry if you want to know more about this.

* 10+ black widow tetra - was told a school of 5 was enough - in fact I think thats somewhere on this forum

If I had seen someone say this to you, I would have probably given then a bollocking. See Cory comment for reasoning and remember that most of these fish live in groups of a few 100 to a tens of thousands in the wild.

* 10+ rummy nose tetra - being increased to 6 once the harlequins go, slowly increasing my numbers to 10

While normally, I say 6 is the absolute minimum, this is one of the exceptions to the rule where I say 10 is the absolute minimum because of their behaviour.

* 2m 2f or 3 of one sex blue rams - I had 2 of each but lost one as it was added earlier than the rest while my water was not right, my mistake ! I have 2 Female and 1 Male, waiting for more stock at the LFS (Wednesday) to buy a replacement

Be careful about introducing another male into the tank, it might be worth rearranging décor slightly so that they all have to establish new territories.

ill just add all my fish are healthy, and all get on, I have had no trouble apart from - the guppys fighting with themselves 2 week ago and nipping fins - which they have now stopped.

They might look healthy now, but some of the things I mentioned will help your fish in the longer term. For things like group sizes, it's always best to experience seeing your fish in larger groups yourself before dismissing it.

as for long term plans - 5/6 foot tank (keeping this 3ft 180L at the same time) and also looking at a 240L (roughly) which in the end will be for blue rams mainly

That sounds great. Keep in mind that rams need territories, so you probably want to aim at a long, shallow tank over a short, tall one.

temp 25-26 (ish) depends how warm the room is in general

You don't have a heater in your tank? (assumption based on the idea that the temp fluctuates depending on the room temp. If it does, you're really only supposed to have like... Goldfish in there.)

German Blue Rams are actually pretty fragile as you may have experienced with the one that passed. While your pH and nitrate are at a good low for them (and the ammonia and nitrite are 0 which is always a good thing) GBR's really should be kept at a stable temp of 82-86 degrees F, (27-30C, I believe) the low end of the spectrum will be good for the betta, and tolerable for the others, but not recommended for them long term. This is why I really don't recommend GBR's to people, they're fragile and like a water quality that not much others will prefer, thus limiting the types of fish you can stock with them.

Keeping some fish at room temperature is not a problem, especially if they come from areas where their temperature will fluctuate on a day-to-day basis, but given that no one can monitor water temperatures *all* the time, it is always best to have a heater (even if it is set at 24C in a 25C room) *just in case* something goes wrong, to prevent the water chilling too much. I also consider it quite important to have thermometers so that I can actually check the temperature of the tank. Alcohol thermometers are relatively accurate and usually cost only 1-2 GBP.
I, personally, have never had problems keeping blue rams at lower temperatures (around 25C) than is generally recommended, nor have I found it any different keeping them at higher temperatures. One just needs to be aware that their rate of metabolism is slower in lower temperatures, so take extra care to not expose them to diseases, etc, which one should be doing anyway (regardless of what species the fish is).