Hello; Allow me to add to the confusion. Not on purpose but. I do not have a clear idea of what is going on with the OP's tank.
First thing is the OP seems to have latched onto SAFE as the cause of the problem and may not be considering anything else. A notion came to me as I read the thread.
The problem appears to be ammonia in the tank around three days after a WC and use of too much SAFE. The SAFE should not make any ammonia regardless.
My first guess being the tank is not cycled. A scenario came to mind from a recent thread. has to do with large WC interrupting the cycle process. Here is the information about the idea.
https://www.monsterfishkeepers.com/forums/threads/help-a-newbie-cycle-his-tank.694773/page-2#post-7833758
not another new tank (MFK member)
“Its a
balance between food for the bacteria which as you know comes via the fish just breathing and pooing or something dead and the bacteria multiplication process. Just adding bacteria from any source at the start of the cycle results in dead bacteria as they have no food until the NH3 rises. How long does that take?? Many factors. But the bacteria you added at the start via whatever means will be mostly dead as its had no food, so your NH3 hits the roof and people think how come?? Now, converting NH3 to NO2 is the easypeasy one. The problem is NO2 to Nitrate, now the bacteria that converts NH3 to NO2 is killed by high levels of NH3 and can take weeks whilst they multiply to sufficient level, all the time your fish are in this toxic mix of fluctuating levels.”
“If you stop the process by doing a water change your right back to the start. I like the oldest method, get it all up and running, pop in a prawn or part of one. WAIT until your NH3 hits the high mark on your test kit and then add the bacteria in the bottle form, no nasty's from anyone else's tank. And then wait, do not remove the prawn let it be and keep testing. Your NH3 will drop fast because the bacteria is everywhere in the air around the world (good old mother nature hey) and now your into the long wait until the NO2 drop and remember you have to feed them or they will die. As soon as the NO2 drop pop in your fish and monitor. At the nd of the day there is no easy/fast way.”
“If you remove the food which you are doing with a WC by dropping the NO3 and/or No2 how can the bacteria multiply?? You are going back to a clean system or at the very least dropping the food levels, no/reduced food means slower or even stopping the cycle dead. And in the worst case in which you do a WC and remove the food as well the bacteria will die = back to the start. If you read the blogs people can take months to cycle their tanks because they pop in fish and then see the levels go through the roof. At this point you loose your fish or do a WC and stop and stop the cycle and this goes on and on and on and on.”
Another idea is that the big overdose of SAFE acting as a reducing agent may possibly be killing off some of the beneficial bacteria (bb). Have no particular reason behind this idea. Throwing it out to be taken apart if faulty.
Last thing being the tank is way overstocked.
I think RD has been hitting these ideas , or at least his posts got me to them. I respect RD's comments.