had a look at the fish you said and do like the look of most of them. Would I be safe in thinking about 6 of each of them would be my limit for the tank or can I go for more or less of a species.
Most of the fish JD mentioned are shoaling fish. This means the fish has evolved to require a largish group. There can be specific reasons for this, depending upon species, but it is a definite fact that shoaling fish absolutely must be kept in a group, at least to start with, if they are to be in the best of health. The number in the group sometimes depends upon the species, as some need more than others, but in general, the more the better. So, while one may read "minimum six" or something, always keep in mind that when you have the space, more than six will be better for the fish. This means better health, which means more natural behaviours, which means more interest and enjoyment for you when observing them.
In general, all characins (tetra, pencilfish, hatchetfish) are shoaling; most cyprinids (rasboras, danios, barbs, loaches) are shoaling; and many catfish (corydoras, etc) are shoaling. With the sized tank you have, I would recommend around 9-12 of most of these, though again the species may warrant less or more.
like the look of ruby sharks say they grow to a max of 12cm about 5 inch would 4 be ok to keep in the tank?
http
/www.aquaticst...Ruby-Shark.html
This is another "problem" fish. The species is Epalzeorhynchos frenatus, and another common name is Rainbow Shark. A shoaling fish technically, but here we have an example of a fish that within the confines of an aquarium does not have the expanse of its natural habitat, and it can change somewhat. It is territorial and combative with its own species, and thus best kept in solitude (as they seem to live in their habitat). Young fish tend to be secretive, but as they mature some can become aggressive, especially with their own or similar species. This "shark" will get along with some of the loaches (Botia sp.) but other bottom fish should be avoided. Upper fish such as the medium barbs, rasbora and danios would be suitable, but tankmates need to be carefully chosen. In other words, adding one of these to your tank might well create real trouble. As often occurs with such fish, an individual in one situation may seem fine, but other individuals may be real terrors and kill other fish. It is best to assume that the fish will be "normal," rather than risking it.
This is a fish that would work well in your sized tank, as a mated/bonded pair. Males/females must select their mates, or trouble may ensue. But the main issue here is temperature. This species needs more warmth than many other tropical fishes, around 28C/80-82F minimum. So finding tankmates must take this into account; some fish kept this warm will literally burn themselves out because the temperature of the water governs the physiological operation of fish. Unlike mammals, they cannot regulate their internal workings when the water temperature lowers or falls outside their preference for a healthy life.
A nice peaceful shoaling fish, and one that will be best at more moderate temperatures for example, around 75-77F/24-25C. A couple degrees may not look like much, but when it comes to the physiology of a fish, it is very important.
Byron.
