Topic

Tropical
Freshwater

Coldwater
Freshwater

Tropical
Marine

More difficult, especially when breeding quality strains.
Can be kept in outdoor ponds or indoor aquariums.
Generally hardy and tolerant of water condition changes if gradual.

A very disciplined approach required to maintain top quality water conditions at all times.
Quite intolerant of varying water conditions.
Some species are
'only one specimen per tank' suitable or may be invertebrate-eaters.

Widespread

Live-bearing and egg-laying species available

May be difficult to find really high quality varieties except through specialist outlets or Goldfish/Koi Societies.

Licences are needed for some
non-native coldwater species.
(details)

Increasing all the time
(Invertebrate stocks included)

Most marine outlets give expert advice for beginners but avoid high-cost 'exotics' which may have very specific, non-sustainable feeding needs.

Number of fish
in any given volume

Maximum

allow 75 cm² water surface area per 2.5cm body length (excluding tail)
or 12 in² per inch of fish

Suggested minimum tank size:

60 x 38 x 30 cms
(24" x 15" x 12")

Moderate

allow 190 cm² water surface area per 1cm body length (excluding tail)
or 30 in² per inch of fish

Suggested minimum tank size:

90 x 38 x 30 cms
(36" x 15" x 12")

Minimal

allow 300 cm² water surface area per 2.5cm body length (excluding tail)
or 48 in² per inch of fish

Suggested minimum tank size:

120 x 45 x 45 cms
(48" x 18" x 18")

Aquatic Plants

Yes
Very wide range available including very realistic plastic replicas for use with herbivorous species.

Yes
Colourful aquatic plants and pondside, moisture-loving plants also available for outdoor fishkeeping.

No
Macro-algae, soft and hard corals culture possible but these are usually dependent on high-intensity lighting to thrive satisfactorily.

Costs

Reasonable
Complete 'ready-to-go' systems available - just add water, decorations and plants and plug in.

Reasonable
Increases rapidly if Koi are to be kept.
Quality of pond-lining materials proportionate with price.

High
Completely automated systems available - at a price!
Salt mixes (for water changes) an ongoing expense.

Thermostat/heaters, power filters, airpumps, thermometer, fluorescent lighting

Power filters, airpumps, fluorescent lighting.
Additionally, pond pumps, liners, filters, UV units will be needed for outdoor fishkeeping.

Thermostat/heaters, power filters, protein skimmer, extra powerheads, calcium reactor. Fluorescent (white and actinic) and/or metal halide lighting (especially for invertebrates);
Reverse Osmosis (or Nitragon) unit to ensure pure source water, hydrometer. Living Rock.

Breeding Possible?

Yes - large number of
co-operative species
Diverse methods of reproduction
Many species of egglayers exhibit parental care

Yes (often unnoticed in ponds until fry seen) but can be very specialised when raising specific varieties
'Hand-stripping' (manual extraction of eggs and milt from individual fishes) often used for twin-tailed species

Yes - but generally only with smaller species such as Clownfish, Gobies, Cardinalfish; the real 'exotics' have yet to be cracked and best left in the sea (or public aquaria).

Society Support

Yes - widespread

Yes - Specialist Goldfish and Koi Groups

Yes - but only a few active groups.

Literature

Plenty of books and monthly magazines

A few books on Goldfish, plenty on Koi but only one exclusive magazine outside specialist Societies

Plenty of books and at least one exclusive magazine