I'm new to aquariums (and don't yet have one, I'm trying to gather as much information as I can before taking the plunge).
I've space for a tank up to about 30 UK gallons/130L (really no larger than 28"x18"18" or so). I might be able to go bigger, but not much more.
I'd cycle it without fish before stocking it, and reading around on the various care sheets and on other forums I've narrowed it down to a couple of options to explore (i.e. "rule out completely") first- chosen on the basis that they seemed reasonably easy and interesting- the Weather Loaches or Blind Cave Tetras. They wouldn't be sharing the tank with any other species.
I've several questions-
I'm finding conflicting information on water volumes- the caresheet here says 300L (66 gal) for the minimum tank size, whereas others suggest between 10 and 80L 30+ seems to be commonly quoted). I understand they can get quite large and should be kept in a group (I was thinking I'd be able to keep 3), but which do I believe?
Being a bottom living fish, will a 24"x18" footprint be large enough? Or is this why some of the suggested tank sizes are so large?
With the tetras, I've seen it suggested that they'll be OK without heating- but is that going to be true in a UK winter? (The house gets quite cold at times- especially at night- certainly less than 16 degrees C).
Given how hard the water in London is are either species going to have a hard time with the water chemistry?
If you have any other advice and experience I'd be pleased to hear it. Thanks in advance. :)
Space is something that is only relatively recently being given much thought in relation to fish welfare. Many sites will recommend a tank volume based on the fishes waste production of just it's size with no thought to it's mental well-being or the physical exercise it requires for a long and happy life. We try very hard on this site to give tank sizes that ensure all the fishes welfare needs can be met, rather just just enough to keep it alive. Kept like this the fish are far more interesting displaying more of their natural behaviour and showing more individual personality.
The blind cave tetra (Astyanax mexicanus) normally gets to about 8cm/3in but can grow to 12cm/5in so we would always recommend you assume worst case and stock the tank as if they will all grow to 5inches. We know from research that fish can count the size of a shoal to a point. 1,2,3,4,5, many seems to be their counting method. So you need many, after that they can only really tell as the shoal doubles in size. This is why we recommend 6 for shoaling fish. For temperature - although it is subtropical you should have a heater in the tank to stop the temperature dropping too low. These heaters are thermostatically controlled so even in goldfish tanks they're a good idea just in case the room gets cold one winters day. I did a little bit of research on fishbase.org to check their natural habitat with regards to PH but unfortunately it came up empty - then their database crashed . PH and water hardness is important to the osmotic pressure on the fishes gills. Keeping a fish in the wrong PH does do it harm over the long term and should be avoided, it's to do with genetic design and cannot be overcome by a few hours acclimatisation!