Oh I don't mind the 7.5 liter tank, that's fine but you really should find a new home for your Zebra Danios. You are going to stress out both fish and end up with more sick fish and that's never fun!
AQ salt you can get any brand, doesn't matter as long as it is marked Aquarium salt. You can also use Rock Salt but NEEDS to be PURE NaCl, no caking additives or any others.
As for heater, I really like this heater: http://www.drsfostersmith.com/produc...8&pcatid=11368
Get the 25Watt one. This way you can change your temp when you want to and especially for medical reasons like Ich and Velvet cannot survive in high temps so you raise the temp to kill it off ^_^
With that heater though, use a bucket and let it work over night to make sure that it can retain a stable Temp level, you don't want to fry your fish either! I also suggest you invest in a glass thermometer, it's going to make your life a heck of a lot easier. So when you put it in the tank, put it at it's lowest setting and let it adjust to the water, then over a few hours raise the temp until your thermometer
say's 78-80, not the heater. Because in smaller tanks the heater will overcompensate and think that's it's heating at 80 when it's really heating at like 85-86 lol so go by the thermometer not the heater indication.
Also acclimating is a little more in depth than just letting him get used to the temp. What you want to do is get him used to the water quality as well and you're going to have to do this for when you do water changes as well.
Here's some steps to follow for acclimating well:
- Scoop Betta out with a cup (one that has not seen soap, any plastic will do)(solid colored cups reduce stress because they cannot see where they are so it actually calms them down)
- Change out water either by dumping it all for a 100% or siphoning half of it out.
- Replace water and let your Betta float in the water in the cup.
- Tablespoon in 2-3 spoons of new water into the cup every 10-15 minutes.
- Repeat above step until an hour has passed.
- Finally gently tip cup and let Betta swim out, he is now used to the water chemistry.
You'd be surprised at how much the water chemistry changes from water change and to each week. So acclimating them is very important so that they don't go into shock.
As for a fin rot treatment here you go:
- Measure out 1 teaspoon per gallon of water/3.8 liters of water. (your tank is a 2 gallon tank so measure out 2 teaspoons of water)
- Place salt in a plastic cup with some tank water in it, mix until COMPLETELY dissolved. (If you do not dissolve the salt, while it melts in the water it actually makes and gives off heat so it can burn your Betta)
- Dribble a little bit of salt into the tank every 15 minutes until all is in.
- Everyday do a 100% change on the tank (scoop Betta out and dump water)
- Refill with same temp water and use your conditioner *Note* you can run a glass thermometer under your tap so that you can get it exactly at the temp that you need!
- Re-add salt, salt does not evaporate so you take it out physically with a water change. Now that you changed your water, re-add 2 teaspoons of salt. (Dissolve it and add to water)
- Float Betta in his cup in the water, tablespoon in 2-3 spoons of new water to his cup so he can get used to the salt.
- Gently release Betta into tank.
- Repeat steps for 7-10 days or until fin rot is gone.
Note*** DO NOT use AQ salt for more than 14 days as it can result in liver/kidney failure but otherwise perfectly fine at this dose till 14 days.
The most important part is the water changes, it's going to keep him healthy. Also you really need to get rid of the Danios, they aren't meant for small tanks and they're going to get stressed and most likely nip your Betta. For normal water changes a week you should be doing 2 100% water changes in a week to maintain that tank properly.
EDIT: also sorry for converting everything.