30 Gallon Tank Guppy Help! His behaviour has changed

My guppy fish stays at the bottom of the tank and hardly moves. I have a 30L tank of 8 male guppies and a pleco. I’ve just tried to feed them and he’s gone to try and find food and started ‘spinning’ frantically and looked out of control. All the other fish are fine. Help! There are no spots or marks on him

 

Was your tank cycled before adding the fish?
30L as in 30 liters or 30 gallon long?
Do you know your water parameters?
Is that the only symptom? Has he stopped?

 

My tank was cycled for 2 weeks before i added any fish. They have all been in the tank for around 7 weeks now. I’ve tested the water and everything is fine. That’s the only symptom he is showing, but he has stopped coming to the top to eat.

 

My tank was cycled for 2 weeks before i added any fish. They have all been in the tank for around 7 weeks now. I’ve tested the water and everything is fine. That’s the only symptom he is showing, but he has stopped coming to the top to eat.

Had this happen to one of my guppies not too long ago, some causes you could check are
Water Parameter
Temperature change
Lack of Oxygen
Stressful Environment
Swim Bladder Disease

I unfortunately couldn't fix it fast enough and my guppy died, hopefully it's not too late!

 

My tank was cycled for 2 weeks before i added any fish. They have all been in the tank for around 7 weeks now. I’ve tested the water and everything is fine. That’s the only symptom he is showing, but he has stopped coming to the top to eat.

Can you explain what you mean when you say your tank was cycled for 2 weeks before adding fish?

How did you cycle it? Do you know your exact water parameters (ammonia, nitrites and nitrates)?