HI Yashwant,
This is Rohan from Mumbai.
On 22 October i purchased flowerhorn fish. in the shop & for One week he was very active, eating okiko head huncher pallets. From 29 October i started feeding him AIM dried shrimps for at least 4 to 5 days. He was loving dried shrimps.
My feeding for him was morning 2 dried shrimps 4 pallets, Evening 6 pallets & night 6 to 8 pallets. he was eating very well.
But from 4 November afternoon he stopped eating. started white stringy poop from his anal. food which he used to like he spit & don’t eat it later.
Current Condition of my Flower Horn =
1 – He’s not eating.
2 – Not active as earlier.
3 – No bloated tummy as other flowerhorn has in this condition.
Remedies i tried after google =
I kept fish in 1 and half feet tank. My Tank temperature is 32 to 36 degree Celsius.
1 – On 6 November tried Metronidazole 450 mg to put directly in fish stomach by insulin injection method (removed syringe). Completely failed as it was very dangerous & difficult. didn’t try after that.
2 – On 7, 8 & 9 November crushed 1 tablet of Metronidazole 450 mg & putted in tank. all three days i changed almost 60% water. 
3 – Today (10 November) Followed the same as last three days. but today i tried soaking pallets in Metronidazole 450 mg mixture & then i feed him. out of 4 pallets he ate 2 pallets (few part he spit out).
From the time i brought him i never fed him with live food. As you said because of High Protein food cause to worms in stomach of fish.
As i said i cant to Injection method to cure my Fish.
What am i following is right?
Will it cure my Fish?
Please suggest if i am doing something wrong & most important how i can i cure him.