Somehow, I doubt highly that your mom doesn't have bleach in her laundry room..that is like a staple in that room. You'd just use regular household bleach to clean it with. Bleach evaporates extremely quickly...so if you sit the tank outside where it's warm...it will evaporate in a couple of hours.
Bettas are not "minimal" waste producers in the slightest..they are big time poopers, very messy fish (which is why people ***** about the cups at WM all teh time..cas they are always full of poop). And ammonia doesn't just come from poop. It comes from uneated food and pee...fish don't just poop.
Even though you can't see it doesn't mean it's not there.
I don't see how their could be an infection in the tank when one died of constipation and another was fine in the tank until he started biting his fins and I removed him and before the fish that was biting his fins and the one that died of constipation the previous fish was a paradise fish but he died because he jumped out of the tank and dried up before I found him and the one before that was a long finned rosy barb and he got stuck on the intake thing of the filter and died and the one before that was a betta that might of died of old age because he was in their for awhile.
Ok...1st.
A fish dying from constipation means he most probably died from a bacterial infection, from the decomposing waste inside his/her body. You need to nuke the tank to rid the tank of anything that could be left lingering about, especailly if the dead fish stayed in the tank for a day or more. That's just gross to not clean it.
Hot water won't do the trick..because you aren't going to get the water hot enough to kill whatever may be in it.
How would you feel going to the dentist and him using the same tools he just used on a previous patient who had a contagious disease...but he washed it in hot water in the back sink before he was gonna use it on you? I doubt you'd feel comfortable with that..and if you would..you need your head checked. I'd think you would definately want that item placed in the autoclave for thorough cleaning.
2nd...
Your thread is extremely misleading. If you've actually only had 1 fish die in this tank. You're being wishy-washy, and now I don't know whether to believe you or not. Either the fish are dying because you keep putting them in that tank..or they are dying for other reasons...which is it?
Sounds to me like you need to put a lid on the tank and your fish would simply quit dying..from jumping out of it.
Fish 1 - betta, died from possible old age
Fish 2 - rosy barb, died from being stuck in filter
Fish 3 - paradise fish, had constipation but actually died from jumping out of tank
Fish 4 - betta, did not die but was biting fins
Fish 5 - betta, died from constipation
So exactly what was the purpose of this thread "
Why Do My Bettas Keep Dying In My 2.5g" when bettas/fish dying isn't actually the case??? I'm confused