rabbut
I don't bite, all that often...
After doing a bit of research I've decided on
A few Cardinal Tetra's
A few Harlequin Rasbora's
and a Flying Fox or shark of some sort?
These good choices? Will the Flying Fox be aggressive towards the tetra's and rasbora's?
Cardinals and harlequins are both excelent choices A single flying fox would be OK I'd have thought, but Ihaven't kept them before so don't know for shure. I don't know of any sharks small enough for a tank of that size. The smallest one that springs to mind would be the red tailed black shark or Ruby shark, both of which can reach over a foot in length (I'v seen both at just past a foot)
apparently tiny fish like tetras are very hard to keep they need a particular water balance of acidity etc,
LMAO Tetras are one of the most addaptive to "different to their natural" water conditions, when compaired with most other fish I have ever kept. I doubt highly that a high pH would upset them at all, so long as they were acclimetised correctly. Poorly bread fish may struggle to adapt, but you would't realy want weak fish like this, as they are IME more suseptable to disease. Good tetras will be perfecly happy and healthy up to pH7.5 IMHO, but I am sure they can adapt to higher.
Having danios as a starter is a good idea - they are good for starting the nitrogen cycle and aren't thay fussy when it comes to water. Thats what i started off with anyway.
I agree that keeping danios as your first fish is a good idea, being very hardy and forgiving of errors in maintanance. Please don't "start the nitrogen cycle" with them, as IMO this is cruelty to animals. This process intentionaly exposes them to ammonia and nitrite that will damage their long-tearm health at best kill them at worst A fishless cycle is far better for the fish
HTH
Rabbut