I just tried the bathtub technique to introduce my rats.

[Lourice]

Well, it kind of worked...? They didn't fight because they were terrified of the bathtub, but my older rat Maurice hissed at the younger Louis which he hasn't done before. However, I would much rather take a hiss over a fight any day.

Needless to say, we stopped after a few seconds of their bathtub terror and put them back in their cages. This was their second introduction after the first, which was a few days ago, was deemed unsuccessful due to fighting that drew a little bloody scratch on Louis' leg.

What should I do next?

I want to try this again in about an hour, on neutral ground, but on carpet this time. I just want my rats to be best friends already.

 

[SQ]

Have you gone through the steps of having the cages near one another so they can smell eah other but not touch? And exchanged dirty cloths between cages?

If so, then you need to be putting them into the bathtub for 20 to 30 mins at a time,
repeated until they are no longer showing any signs of aggression.
It needs to be 20 to 30 minutes so that their anxiety is decreasing when you end the intro, not still increasing.

 

[hopefloats]

I never put them near each other cage wise for intros. The stress that males get at the cage bars is more than the benefit it will give them. I do switch cages with my b-Rats. If i am not able to switch them out in cages then I switch out litter boxes and food bowls. I will change hammocks around to. To me if a boy is being that bad during an intro a neuter will most likely be needed. I can take fights on common ground you can usually get past them. I have yet to get past a fight on a scary ground that occurs with in a few minutes of meeting. I always prefer switching because the key to them accepting that other rat is to allow their smell in their cage. Rats are more about smelling then visual. I have found that to be a 1000 time more beneficial than anything else. I would personally do that for a few days prior to starting intros it wont be as much of a shell shock to the crabby ones.

 

[jorats]

I've given my advice in the other thread. But It's best to have your own thread going so I will write it out here too.

First off, the size of testicles, will have nothing to do with aggression or non aggression. That's the good news.
When you first put them together, where was the location? On the bed or someplace where both rats have never been? I would suggest using a table top. Put some yummy liquidy food in the middle and add the two rats, nothing more.
The fact that you say Maurice and Louis are both under 3 months, this should be an easy fast intros. Males don't really come into full hormonal maturity until about 4 to 5 months. Sometimes it does start at 3 months but that's not very common. A small nick in the leg, is not reason to think aggression. An aggressive rat will lunge and attack the genitals or the stomach, everything else is pretty minor stuff and a good indication to keep doing intros.
Do your intros in a "new" place, do them for at least 30 minutes long. Always end on a good note, even if they fought. Separate the fight, hand them a treat and then end the intro for that day. If you can do intros several times a day, that's even better. Switch their cages, each day, the boys switch cages, this will get them used to the other guy's smell.
It's true that some rats get extremely stressed out by being near the other boy's cage, so that's something, you'll need to observe and identify and if that's the case, then separate their cage. But since they are so young, I would think it's quite ok in your case.