No amount of gizmos and chemicals are going to make it ok to keep 64 Garra ruffa that should reach ~15cm in ~180l of water. Even a tank in excess of approx. 1000l (yes, one thousand litres) would make it difficult for the average fishkeeper to keep this many moderately sized fish healthy. Does that give you some idea of how badly you are overstocked and shock you? I hope it does, you need to rehome at least 50 of them ASAP.
If you are feeding the fish so each one gets at least the size of one eye per day of food (young growing fish should be getting more than this), even if the tank does not experience ammonia/nitrite spikes, you will be forever battling to stop nitrate reaching toxic levels by doing 80-90% water changes (in one go, not split up which effectively means less of an overall change of water btw) pretty much everyday.
Keeping so many fish will also mean much more frequent cleaning of the filters, instead of about every 3 months, you should be striping them down and rinsing (without too much aggression) something like every fortnight without fail. The filter filter should be caked in faeces from their food, plus no doubt food that was picked up by the intake strainer. The impeller and its cavitity will need a good wipe with cotton buds, again using removed tank water.
This is not about the fish fighting with each other, indeed many garras are very social. It is about them being in good conditions with a manageable maintenance regime for the keeper.