Can I use activated carbon and CO2 injection?

[millsn]

Not for my loach tank but for a planted one in which I have three zebra loach amongst other tiny fish.

Secondly, would the carbon strip out any water borne fertiliser I might add?

[Francois van Brederode]

Active carbon does remove any fertiliser you might add.

Other than that, there is no problem combining carbon with co2.

[Diana]

Activated carbon has that reputation, but it does not 'strip out any fertilizer'. It may remove some organically bound fertilizers, perhaps chelated iron, for example.
AC gets filled with mostly organic molecules within a few days of being added to the filter. Most people leave it in for a month, and for most of that month it is doing nothing but growing nitrifying bacteria.

What are you trying to remove form the tank?

I use AC only in case of emergency, or after medication of a hospital tank to remove the meds. I do not keep AC in the filters all the time.

[millsn]

Hi Diana,
I've no specific objective other than to use up a mountain of the stuff that I've bought! It's a "tap water tank" heavily planted, no issues with it just fancied trying it.

[Marcos Mataratzis]

Hi millsn,

I consider chemical filtration with AC or Purigen as important as others as it will remove lots of undisirable organic compounds from water. I do make use of them 24/7.
As Diana said, it won´t remove most fertilizers, except maybe some colorfull ones.

It´s usage is therefore indicated even in planted tanks but I would not have any Botia in a planted tank.