IMO it's a gamble. The RTC may or may not eat the knife.
In most cases, it appears that if the knife or any tank mate for that matter is hard for an RTC to wrap its mouth around, it is safe but reports of "rogue" RTCs abound too. Also, the smaller the enclosure, the exponentially higher the chances of predation by RTC.
If the knife is most obviously way too big for the RTC to swallow, it's usually quite safe, albeit there are rare exceptions where an RTC will still try and choke or injure the prey.
On the other hand, knifes are predators too. A big knife will scarf up a small RTC no problem. Knife's collapsible mouths appear deceivingly small. That's why they are so flat. Stealth. When viewed by prey head on, knifes look like a thin small fish with a small mouth. Oh, but it is not... Same with TSN.
In most cases, it appears that if the knife or any tank mate for that matter is hard for an RTC to wrap its mouth around, it is safe but reports of "rogue" RTCs abound too. Also, the smaller the enclosure, the exponentially higher the chances of predation by RTC.
If the knife is most obviously way too big for the RTC to swallow, it's usually quite safe, albeit there are rare exceptions where an RTC will still try and choke or injure the prey.
On the other hand, knifes are predators too. A big knife will scarf up a small RTC no problem. Knife's collapsible mouths appear deceivingly small. That's why they are so flat. Stealth. When viewed by prey head on, knifes look like a thin small fish with a small mouth. Oh, but it is not... Same with TSN.
