I would like to change substrate in my 25L tank but I do not know how to do it properly. I have some Oliver Knott and Akvastabil haley mix in it, but I would like to change it for Lava sand. There are lot of Neocaridinas in this tank. Is it possible to do it at once or part by part? I do not want to empty my tank. Can I siphon old substrate out and but a new back?

I read shrimpy daddy article of Preparation Process for Lava sand and how to age it. There was instruction: Soak the material in warm water (40 to 50C) mixed with diluted acid/chelating agent for 1 to 3 days. What type of acid I can use? Can I use ordinary vinegar? How weak is this solution should be?