Hi Pratik and welcome.

May be best to provide some further information.
Most balanced AP systems would not require a lot of inputs unless the fish load is limited.

(a) why do you want calcium
(b) why calcium nitrate specifically
(c) what is the pH of your system and how hard is it (KH/GH)
(d) what is the current ammonia, nitrite and nitrate level of your system
(e) how many and what type of fish do you have ?

are you trying to run your AP system like a hydroponic system ?

you would be better running the system with an organic liquid fertiliser rather than trying to balance elements or go down a hydroponics path.

If you can source it a liquid seaweed with low nitrogen (N) and phosphorous (P) is ideal.
Many new systems need a dose to keep plants going early on.

what do you have access to locally ?

Early on you can use something with a litle bit of N & P - ie. most liquid fertilisers.
But don't get products with high N/P .

IMO safest way to apply is to mix up in a watering can at half strength and water direct onto the grow bed.
It involves less risk for the fish.
But others here add small amount direct to sump/fish tank.