Cherry Barb laying on tank bottom for past few hours. HELP

[Darkless]

My Cherry Barb is currently laying at the bottom of the tank and only swims for a few seconds every now and then, but I have seen this steadily decrease to the point where she only responds and floats up a bit if the tank is moved slightly, or if the light is turned on. My female Cherry Barb, who is around 6-7 years old, is the only fish currently in my 2.5 gallon tank. Before this happened, I had suddenly begun to see her swimming at the back-right corner of the tank, below where the filter is. The tank hasn't been cleaned in a few months but it will be cleaned today. I have tried to use Tetra Easy pH balance, and right after I used it, she shot up from the bottom of the tank and swam for a little bit, but proceeded to lay back at the bottom of the tank. She is currently laying near the back-left of the tank, near the bubble stone. I'm not sure if this is because of her age, the water quality, or if it's a combination of both. I will also mention we recently just moved into our current house about 5 weeks ago, though she has been acting normally even after being moved in. This has been going on for about 2 days now. Any help would be appreciated, and I will attempt to provide any information needed. Apologies for the lower quality of the pictures.

 

[Rocky998]

There are a ton of issues I see... I actually don't have time right now to go through it all...

But let me just give a run down:

1) Blue lights are stressful for freshwater fish
2) tank is way too small
3) barbs have to be in groups when their alone their stressed
4) Don't use any pH buffer like that. Some can be harmful
5) I see no hiding spots for top-mid dwelling fish like cherry barbs. I recommend getting either very soft fake silk/soft rubber plants that are meant for aquarium or your best option is to get real live plants.

@GaryE Maybe you can help a bit? I feel like I don't have the knowledge to walk them through all of this

 

[Byron]

We will need more information. What do you mean exactly by "tank hasn't been cleaned in a few months"? Do you do regular partial water changes? Do you vacuum into the gravel? What are the water parameters, which refer to hardness (GH), pH and temperature? Have you tested for ammonia, nitrite and/or nitrate, and if yes, what were the numbers?

The points made in post #2 are certainly relevant, but w need this additional information. And I will be honest, we will hopefully be able to point out the problems for the future to avoid but not likely to save the fish at this stage, given your description.