The killifish website said you can hatch the eggs in take away containers - if you've got an air pump to keep the water oxygenated. Not having any such thing it seemed wiser to shell out another 24 quid for one of these http://www.seapets.co.uk/products/aquarium-supplies/aquariums/plastic-aquariums/water-world-aquarium-kit-by-penn-plax.html and attempt to justify it to myself by pretending that it'll come in handy later on as a quarantine tank for medicating sick fish, or a secluded breeding chamber for romantic fishie trysts.
Meanwhile I'm not doing a very good job of looking after the aquatic plants. They're such wimps! You can't hardly touch them without the leaves bruising, and then they start to rot. I've gone right off pretty feathery leaved things, they might look good swaying in the current, but once they start to die and the leaves drop they are a menace. Chasing floating fragments of decomposing plant up and down the tank with the little net on a stick churns up the water, and then the other not-yet-rooted-into-the-substrate plants to go floating off, and it's devilish hard to catch and replant them without bruising their leaves, which then rot and have to be chased around the tank with the little net on a stick...
You're supposed to go over it every day and snip off any leaves that are starting to look a bit past their prime. I've snipped off so much that the tank is starting to look bare. Poor frail plants, massacred by brutal handling and pH spikes. Turns out Swansea valley water has very low carbonate hardness and this somehow means that the water pH isn't properly buffered and easily goes scooting off up and down the scale in response to slight changes that wouldn't make much difference to other kinds of water. I've been trying to read up on it, but find all the details about KH and GH and TH slippery and annoying.
Anyhow, you can't have an underwater garden without any plants, so I cheered myself up by ordering a load more. I'm getting them in pots this time, so that they can be hidden in the gravel with a minimum of handling. A couple of little ferns, a miniature sword plant, some baby tears, more water wisteria, more moss, some plants that float on top of the water, and a red lotus. They won't arrive until this time next week, so I have plenty of time to learn how to keep the water parameters steady before then. Got to have loads of leafy shelter to welcome the fishes when they arrive.