Hi...newbie With Loads Of Questions

Firstly, thank goodness for this forum! I thought I would struggle through this whole process killing fish more by accident than design.

My wife has bought me a biorb 15 for Christmas after me telling her how much I loved having tanks as a kid (my Dad's tanks not mine).

Obviously this thing is tiny and not brilliant by all accounts so I was looking at getting something slightly bigger (Aquanano 40/55l) which I can get in my small living room.

I know I need to do a fishless cycle which I've seen the advice on here (although I'm still a bit perplexed) and will also get an API kit and hopefully set in up over the next two months.

But  actually wondering what I could stock in it? The calculator i used reckons 21 slender fish. I was thinking:-

1 dwarf gourami or 2 Congo tetras
6 cardinal tetras
3 guppies
3-5 Red cherry shrimp or blue ones

I was also wondering if people have to Aquanano 40 and if it is any good can you suggest something of a similar size and dimension...along with how you've aquascaped yours?

Any advice would be greatly appreciated!

Cheers
Rob

Calculators that say x fish for any particular tank should be avoided. The old guideline was 1 inch of adult sized fish per American gallon, ie per 3.75 litres. And that only applied to narrow bodies fish up to three inches long. By that rule, a 15 litre biorb can hold a max of 4 inches of fish, and a 55 litre tank 14.5 inches of fish. That's not the number of fish but the total size they grow to.


The fish in your list:
Congo tetras are quite big fish (males up to 8cm, females 6) and they are fast swimmers. They need a tank at least 48 inches/122cm long. They are also shoaling fish so you'd need more than 2 of them.
Dwarf gouramis would fit in a 55 litre tank. However, a lot of them are infected with dwarf gourami disease before they arrive in the country from farms in the far east, and they commonly die within a couple of months. A better choice for a 55 litre tank is the honey gourami. Some shops insist on calling them honey dwarf gouramis but dwarfs and honeys are two separate species.
You might get away with cardinals in a 55 litre tank, though they'd be better in a tank at least 60cm long.
Guppies would be fine in a 55 litre, preferably if you have hard water. But these fish have been very inbred making them quite weak fish. Keep only males; if you have males and females (which must be kept as at least 2 females for every male) you'd be knee deep in fry in next to no time.
Shrimps - fine in a 55 litre and the 15 litre biorb. Stick to one colour as blue and red are the same species and will interbreed giving you a tank of brown shrimp.

A 15 litre biorb is a very difficult tank to stock. Does it have a heater? If it does, it would make a good shrimp tank and with no fish to eat the baby shrimp you could have a nice colony of them in there.

For a 55-ish litre tank, there are quite a few small fish to choose from, depending on if your water is soft or hard - your water company's website should have that info somewhere. Although many fish will cope with water outside their preferred hardness, they will be happier in water nearer their preference.

I like this website for checking a particular fish's water preferences and tank size. It has more entries than the fish profiles on here, and it gives more info. For a 60 cm long tank look at -
For soft water - ember tetras, chili rasboras, Microdevario.
For hard water - endlers (male only, they breed like rabbits as for guppies!), emerald rasboras

My shrimps are on sand so I don't see any issues with fluorite - unless anyone who has it knows any different. If you want to use the biorb for shrimps though you'll have to use the 'rocks' that come with it as those are actually part of the filter.

pH can change on standing. It is common practice for water companies to pump carbon dioxide into the mains water as this discourages limescale build up. This lowers the pH artificially. Once it is exposed to air, the carbon dioxide gasses off and the pH rises to its 'normal' level. The amount of change depends on how much carbon dioxide was added. Leave a glass of water to stand for 24 hours and test again.
Substrate usually has the effect of raising both pH and hardness. Some types are made from crushed coral or limestone. These are both calcium carbonate which dissolves slowly in water putting calcium into the water (ie raising general hardness or GH) and putting carbonate into the water (measured as carbonate hardness or KH). When they dissolve in water they also increase pH. The way to find out if you have one of these substrates is to drop a bit of acid on a pinch of it - vinegar is fine for this - and if small bubbles appear, the substrate is made from calcium carbonate.

Does ST give a number for the hardness? If it does, what is the number, and also the unit - it's like feet and inches versus metres only worse as there are half a dozen possible units.
Hardness is more important than pH. It is easier for fish to adjust to the 'wrong' pH than to the 'wrong' hardness. I have moderately soft water with a pH of 7.5 ish and I can keep soft, acid water fish better than hard, alkaline water fish.


I'll let the plant experts help with that aspect. I am getting more into plants but just the very easy kind.