How to minimise fish stress during lights on

[Sudipto]

I have a two feet heavily planted tank with 7 rummy noses and three otos. I keep the tank wrapped in a piece of black cloth during the day (the top remains open) because there are a few windows in my room and it is quite well lit with natural light outside. In the evening when I come back from work I take the black cloth off. After some time I switch on CO2 and then one of the T5 HO lights. My fish react with a start. They run helter skelter for some time. The rummy noses seem to be particularly stressed with their colour looking pale and running around. However, they settle down within some time. After about an hour or so I switch on the second light. But this time the fish don't react.

Obviously the fish is under some stress when the first light is turned on. In nature they must be used to a more gradual lighting up of the environment. My question is how do I minimise this stress in the tank? I am particularly concerned because the other day immediately after switch on, one of the rummies jumped out of the tank. Luckily I could collect it with my palm off the floor and transfer it back to the tank within seconds where it behaved normally after some time. But from the next day one fish is missing. Either it could not survive the stress of the jump or it jumped again. I wonder if this was because of the start that they get.

Some help with how you deal with such a situation or if at all it is an issue worth worrying about will be really helpful.

[Apistoinka]

Maybe you could try remove the cloth and let it settle with what ever light they have first.. than switch on ur room light after that than switch on your tank light.

[tetrakid]

I should think that a brightly lit environment is a rare bonus for a tank full of plants. Is there any reason for covering the tank sides with black cloth?

[Sudipto]

I should think that a brightly lit environment is a rare bonus for a tank full of plants. Is there any reason for covering the tank sides with black cloth?

I have had GSA issues on the walls whenever I left them uncovered for a few days. If it was a nature aquarium in the Diana Walstad style then I could use it to my advantage. In fact I plan to set up one shortly, where natural light will play a role. But in the out and out artificial tank that I have I cannot handle natural light. I have had GSA even on the glass wall where there is a window about 20 feet away and we get only diffused sunlight through that window because of a large mango tree just outside :-). Such is the power of sun. I wish I could harness it.
I have a small tank near a window where I keep clippings of tripartita and HM. They just thrive without any dosing or CO2.

[milk_vanilla]

Repositioning your tank perhaps?