Can someone help I’m new to keeping fish due to granddaughter having a tank at home grandad had to have one, water checks completely fine fish had been ok but recently and only recently once light goes on the fish dart to the bottom and breath rapidly And won’t move even after 15 mins . Once light goes off everything back to normal hope you can see by the pic can anyone help me out .dont want to stress the fish .

Help

I can't see the photo, unfortunately, but, in order that we can get a full grasp of the situation and give appropriate advice, can you let us know the following:
* test results for ammonia, nitrite, nitrates, PH (and GH and KH too - ideally from a test kit but, if not, let us know the CaCO3 and German degress hardness readings from your water company's website for your postcode);
* size of tank - dimensions and water volume;
* how you cycled the tank and when the process was completed;
* what fish you have and how many of each species;
* water change regime.

Thanks. :)

Hi I’m not sure of the readings my daughter in law checked them all using water test kit and all readings were fine the problem only starts once light is switched on it never used to happen I’ve had these 3 months now first 2 months they were fine with light on but now as soon as light goes on they seem panicked .

Pics

Lights off

If we can get the actual readings from your daughter-in-law / you, that would be extremely helpful. Readings can seem "fine" but, for example, a tiny amount of ammonia or nitrite over the course of several weeks or a one-off high nitrate reading could be enough to make the fish skittish, and the light being switched on could be "the final straw" which causes this behaviour, if that makes sense. That's why it's really helpful to get the full grasp of the situation to identify or eliminate the possibility of something which may be predisposing the fish to behave like this.

If it does turn out that all other possibilities can be eliminated, and there hasn't been a particular incident which you can think of that may have made them more skittish (e.g. one of the fish or tank inhabitants not being compatible with the others and having terrorised the fish as a one-off event or only starting recently, a sudden loud bang near the tank, a child shouting or running in the vicinity of the tank, complete changing of the filter media causing a new cycle to start, being away for several days in which the light wasn't on at all, the room being in pitch darkness and quiet and then suddenly the main light or the tanklight switched on), then it's extremely odd but not outwith the realms of possibility that they've developed an aversion to the light.

If all the aforementioned possible factors can be eliminated (we can help work out if this is the case if you can answer the questions and I would really encourage this), then it's not a necessity for the fish to have a light by any means - it is a necessity for live plants, though, and cosmetically for humans' enjoyment of the fish. It is also possible to buy timers for LED lights which can create a sunrise and sunset effect which would be less of a shock to them.