Setting Up A New 100L Tank

The Lido is more of a cube than a rectangular tank. You would need to bear in mind that it doesn't have as much horizontal swimming room as a rectangular 100 litre tank and stock accordingly - either small fish or slightly larger ones that don't dash around.


Have you decided against doing a fishless cycle? Admittedly you can't have fish for a month or two, but then you can fully stock the tank as soon as the cycle has finished.

If you do a fish-in cycle as you suggest with six fish, you would not be able to add any more fish until the filter was cycled. Fish-in cycles take longer than fishless so you won't be able to add more fish for several months. When you could add more fish you'd be able to add up to a third of the fish already in the tank roughly every two weeks - that involves testing the water and a week after the ammonia and nitrite levels stay at zero without water changes, add more fish. So if you started with 6, you'd be able to add 2 more fish the same size once the filter was cycled, giving you 8. 2 more next time, giving 10. Then 3 next time, giving 13 and so on.
Don't forget you'd need to test the water at least once a day and do water changes every time you saw a reading for ammonia and/or nitrite above zero durig the cycling process.

Fair enough. From your first post, you realise that even if you do a fishless cycle, if you don't get the full stock immediately on completion you have to stock slowly as for fish-in cycling.

Since that is the way you want to go, you won't need to cycle to 3ppm ammonia as that's for a full tank of fish. I'd use just 1ppm, maybe 1.5. That should be easier as the nitrite levels won't go up nearly so high - and it's high nitrite that potentially can stall a cycle.

That list looks fine but just a couple of comments.

Sparkling gouramis are very hard to sex, you might end up with 2m, 2f or a pair. Males can be a bit aggressive towards each other so keep an eye out for that.
I would up your numbers of ember tetras. I had 6, now I have 11 and they are much more confident. Mind you, they didn't like being in my 50 litre tank at all, they just hid in a huddle at the back. Even with just 6, they came out a lot  more when I moved them to the 125 litre. It could have been that the 50 litre is in the kitchen with a lot of passing traffic.
Platies - all one sex or 1m 2f. Females will give birth roughly every month - and even if you got all females, if they've ever been in with a male they'll be carrying sperm which will last a few months. f you try to save all the fry, you'll be overrun. The best thing to do is nothing - if you have plants (real or synthetic) a fewfry will make it and that will be more than enough.

This is a nice introduction to plants.  Have a read and you may, at least, have some info on which to frame a question or two!

Regards non-fish things, such as substrate, plants and decor:

Substrate:
2cm - Silver Sand
3cm - Rooting
1cm - Nutrient rich
3cm - Rooting
1cm - Gravel
(This could be over the top but I am planning on having only real plants, and a respectable quantity.)

Yep, definitely over-the-top. Silver sand is a bugger (technical term) 'cos it's so fine grained that there's no flow of water through it and can go anaerobic. You really only need all the nutrient substrate stuff if you're going for plants in a big way with fish as a secondary concern. It will be far easier, cheaper and less messy if you use largeish grained sand (pool-filter sand or play sand (not sharp builder's sand)) or buy ~1-2mm smooth gravel and have about 3-4cm of it. You can then shove in root tabs every few months to feed the plants. This way, if you decide to remove a plant, it's roots don't drag a load of soil into your water and you can re-arrange your tank to your heart's content. (Just my humble opinion, of course.)

Pool-filter sand or (well washed) play-pit sand. They're round, smooth and biggish sand grains that allow some water circulation through the substrate.

From reading the above would it be sensible to say that I should go for 4cm deep of 1-2mm substrate