The tank is only 70 gal. I always use carbon. Normally it lasts at least month or two before needing replacement.Assuming the "wrong" silicon such as anti mold silicon was used, the volume of silicon compared to volume of water is miniscule especially for larger tanks. The chemicals used will rapidly degrade under water and several water changes is all that is needed.
Additionally these chemicals are quite large organic (long chain) complex molecules which are very easy to remove with activated carbon.
I say these things to give you some perspective and reassurance.
Right now, after fresh carbon is installed, the fish are ok for 4-5 days, before starting gasping for air.
Do you think replacing carbon weekly will accelerate the removal of the "wrong things" from the silicon?
Did you ever have to deal with this type of things?
I know it's a case-by-case type of things, but how long it'd take to leach out "all the bad things from the silicon"?
I do water changes every 2-4 weeks.
It's hard to tell how many water changes I did in the past 3 months. First it was daily, then every 2-3 days, then weekly and so on.
Last water change break was 1 month because changing water this regularly wasn't helping the cycle.
Shouldn't the bad things have already "flush out" by now?