help needed??(people using sand as substrate, attention)

[headbanger_jib]

i have my FH in a 95(uk)g tank(he likes to stay alone , tries to kill anything that moves in his tank)
with sand as substrate and and a few rocks to use as cave
i feed him 2-3 times a day(one type of food for a day) food sticks, dried shrimp or earthworms or so
haven't added anything in his tank for nearly 2 months or so
and absolutely no feeders
the filteration is 600ltrs/hr and water changes every four days or so

a few weeks ago i saw a red leech like thing on his face which was red in color, i removed the thing and it was too small probably 2-3mm, it moved like a leech too and when i squished it there was blood.
after that i did a 70% water change and added salt to the tank
my FH was acting normal when the worm was attached to it, no flashing or rubbing against anything

today i noticed my FH
rubbing against the rock and on looking closer i found a similar worm but this was green color,
i have added salt one table spoon/ 10g

any one have any ideas what is wrong
do you think i might have to remove the substrate

 

[headbanger_jib]

he always keeps sifting the sand(digging) was pretty aggressive, but now he is active but is not aggressive(this might have been because of a huge net coming down into the tank chasing him around the tank and then hauling him out and removing the worm)
there is no stress at all
as his hump is as it is
he hasn't darkened or anything

 

[dragonfish]

Where did the sand come from? How filtered is your water supply?

 

[headbanger_jib]

Where did the sand come from? How filtered is your water supply?

sand is aquarium sand
got it from the lfs
had added the sand nearly 6 months ago
this tank was used as a grow out for my gars and bichirs for four months before i moved them and put my FH in this tank
had never seen this kind of worms before in that tank

 

[headbanger_jib]

bump

 

[dragonfish]

Do you feed any live foods that this could have come in on?

 

[headbanger_jib]

i have explained everything in the first post
no live foods
no feeders given since he was 3"+
now he is 9"ish or maybe more

 

[cichlid2006]

i have heard of leeches getting frozen with bloodworm and they survive the freezing process and then become a pest in the aquarium but last i heard they only ate us when our hands were in the tank and didnt bother the fish.
freeze dried is the only sure fire method of leech death that i have read about.

 

[headbanger_jib]

i have heard of leeches getting frozen with bloodworm and they survive the freezing process and then become a pest in the aquarium but last i heard they only ate us when our hands were in the tank and didnt bother the fish.
freeze dried is the only sure fire method of leech death that i have read about.

i don't feed him frozen bloodworms
i had tried that when he was an inch or so
but it seems that he didn't like that and after that i never tried feeding him frozen bloodworms

 

[headbanger_jib]

BUMP
i really need some help i saw one more of those kind of worms on him
today and there are dot like scars on his face
there must be someone here who might be able to help