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Rainbowfishes, unlike mammals, are unable to regulate their body temperatures and are thus subject to the temperature in their surrounding environment. Temperature regulates their metabolism and their need to take in nutrients. Therefore the temperature of the fish's environment is a major and even the deciding environmental factor in determining growth rate, metabolism, and nutritional efficiency. In fact, temperature will influence all biological and chemical processes in an aquarium.
Temperature tolerance among rainbowfishes is similar to that for water chemistry. In their natural environment, many are exposed to temperatures that vary considerably. This is dependent on the size and depth of the body of water, water flow, whether exposed to the sun or in shaded rain forest streams, the time of day and the season. The overall range has been reported from a low of 5° to a high of 36° Celsius, and even higher in a shallow body of water exposed to full sun at midday. However, these temperatures are conditions that wild rainbowfishes have to be able to endure to survive and are not recommended for aquarium keeping.
In their natural environment, rainbowfishes can search for more favourable conditions by moving into cooler or warmer water. However, in captivity this is not possible. Each species has a preferred or optimum temperature range where it grows best. At temperatures above or below optimum, their growth is reduced and mortalities may occur at extreme ranges. A temperature range of 20 to 24° Celsius is suggested for general maintenance in captivity while an increase to 28° Celsius can be used for breeding purposes.
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Example: a 200 litre tank in a 20°C room holding the water temp at 25°C, a 50w heater is required. |
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Number of degrees raised above room temperature |
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Aquarium Size
Litres |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
10 |
12 |
|
10 |
1 |
3 |
4 |
5 |
7 |
8 |
10 |
11 |
14 |
17 |
|
20 |
2 |
4 |
6 |
9 |
11 |
13 |
15 |
17 |
22 |
26 |
|
40 |
3 |
7 |
10 |
14 |
17 |
20 |
24 |
28 |
35 |
42 |
|
60 |
4 |
9 |
13 |
18 |
22 |
27 |
31 |
35 |
45 |
54 |
|
80 |
5 |
11 |
16 |
22 |
27 |
33 |
38 |
43 |
54 |
65 |
|
100 |
6 |
13 |
19 |
25 |
31 |
38 |
44 |
50 |
63 |
76 |
|
120 |
7 |
14 |
21 |
28 |
36 |
43 |
50 |
57 |
70 |
85 |
|
150 |
8 |
15 |
25 |
33 |
41 |
50 |
57 |
66 |
83 |
98 |
|
200 |
10 |
20 |
30 |
40 |
50 |
60 |
70 |
80 |
100 |
120 |
|
250 |
12 |
23 |
35 |
46 |
58 |
70 |
80 |
93 |
115 |
140 |
|
400 |
16 |
32 |
48 |
63 |
80 |
95 |
110 |
130 |
160 |
190 |
|
600 |
20 |
40 |
62 |
83 |
104 |
124 |
145 |
166 |
200 |
250 |
|
800 |
25 |
50 |
76 |
100 |
126 |
151 |
176 |
200 |
250 |
300 |
|
1000 |
30 |
60 |
88 |
117 |
146 |
175 |
205 |
235 |
290 |
350 |
© Copyright Adrian R. Tappin
Updated October, 1999.
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