sera guide - Healthy pond fish

42 Further intoxication causes Intoxications may be acute or gradual. Sometimes the only symptom is that the fish startle more easily. A precise diagnosis accor- ding to the behavior and the appearance of the fish is thus often not possible. Therefore proceed very carefully when researching the causes if you observe the fish being unwell and cannot explain it with the usual patho- gens. Also consider unusual causes such as the use of herbicides or insecticides in the garden (they could have entered the pond with the rain) or having used new deco- ration elements that could, for example, be impregnated with toxic substances. Lacking oxygen is likely if the fish suddenly dwell underneath the surface and gasp for air. This can be fatal in extreme cases. Even slight oxygen undersupply may cause defor- mations in young fish. Check the oxygen level with the sera O2-Test. sera O2 plus and sera air plus air pumps provide quick help in case of acute oxygen deficiencies. Water agitation by decorative brook or fountain elements (sera offers numerous attractive alternatives) ensures sufficient aeration. Check the hygienic conditions in the pond as to prevent oxygen deficiencies. A large amount of organic material compiles espe- cially in overstocked, abundantly fed ponds. Its breakdown consumes oxygen. Make sure you siphon off the sludge and remove leaves and decomposing plant parts whenever necessary. Also make sure the filter is well maintained and works effectively (bioactive filter system: sera siporax pond, sera pond filter biostart and sera pond bio nitrivec). Plants enrich the water with oxygen during daytime. However, they as well consume oxygen at night, without sunlight and do not produce any. This may lead to an oxygen deficiency especially in warm summer nights (warm water binds less oxygen than cold water!). Therefore, be sure to provide suffi- cient aeration and effective filtration also at night. Rot processes occur if anaerobic zones form, i.e. regions that are not supplied with oxy- gen. This may, for instance, happen in the fil- ter if the pump fails, or in case of firm, non- aerated bottom ground. Organic material is broken down anaerobically (without oxygen consumption) there. This leads to the forma- 8 Preventing and remedying maintenance mistakes and intoxications