Scomb's are Payara's but they aren't Saber Tooths, they're more commonly referred to as Vampire's while Hydrolycus Aratmatus the most sought after and expensive of the group are called Saber-Tooths. Scombs are usually plagued by sudden death syndrome and that's why they are so inexpensive when compared to Armatus. To the OP the 125 is gonna be too small for the Tiger in the long run, never mind the other's your hoping to add. Also you should have posted this in the Characin section since your asking about Tiger compatibility. The best toothy fish would have to be ATF's, Wolves and Hydrolycus. Though in my experience they don't house well together. Armatus dislike silver fish and the body shape of the Tigers seems to either evoke a highly predatory or territorial reaction. Also the rarer Wolves like a Curupira and the Saber Tooth Armatus seem to really dislike each other and will shred each other when ever the opportunity arises, at least that's been my experience. Armatus in general can be pretty aggressive I luckily have a fairly docile one and still I was unable to co-hab him with a Wolf long term. He does get along well with his current tankmates which he's going on 2 years living with them with no incidents which are American Cichlids and Silver Dollars. If your willing to upgrade I'd go with a group of Armatus as they can be easier to house than Tigers and can make a pretty awesome display. Just be aware they might kill each other too, though I've been able to house 2 together successfully till one got bloat and died. Up till that point they kept territories on the far ends of the tank and would only snip at each other when they got close to each other during feeding times.