Yugioh Ruling Help?

Question

Super ancient Deepsea King Coelacanth 2800 atk 2600 def

Effect - Once per turn, you can discard 1 card to Special Summon as many level 4 or lower Fish Type monsters as possible from your Deck. A Monster special summoned by this effect cannot declare an attack and its effect(s) is negated while on the field. If this card is target by a Spell, Trap, or Monster's effect, you can tibute 1 other fish type monster to negate the affect and destroy that card.

ok lets say i use his affect and bring out 4 fish but one is a golden flying fish ( tribute one other fish on the field to destroy one card on the field) I know if i send it back to my hand and re-summon it i can use his affect but what if i book of moon and put it face down and flip it can i use its affect ???

Answer 1

His effect is still negated with the use of "Book of Moon" simply because it is on the field and still is because of Super Ancient Deepsea King Coelacanth effect(A Monster special summoned by this effect cannot declare an attack and its effect(s) is negated WHILE ON THE FIELD).  The only way to activate it's affect if you resummon it.

Answer 2

It will be negated because of Super Ancent Deepsea King Coalacanth.