Need Help....i Think

So I redid my 10 gallon Betta tank by putting sand down instead of gravel and adding more live plants and decorations. This Betta, Frosty has been loosing his fins slowly and I treated him for fin rot but that didn’t work so what could it be? I just recently added a Harlequin rasboras, a neon tetra, and 2 bronze Corydoras. The Rasboras and the neon don’t have names yet . I’m trying to find a store that has the rasboras in stock but I haven’t had any luck yet. I would like to get 3 more rasboras and 3 more neon tetras but would that be too many? The Betta does just fine with them and sometimes swims with them (not chasing them) so I’m not worried about them get along. I’ve heard good things about pairs of Corydoras so i’m just going to keep two ang not get anymore. I put a sponge over the filter intake worried that it would suck up sand and ruin my filter because of the cory’s “Digging” in the sand but is that necessary? The plants in there are 1 Anubias Frazeri(new),1 Amazon sword, and 2 windelov java ferns(new). Do I need to get a fluorescent light? The tank gets sunlight because it’s next to a window. Last question, I took a stick and kinda carved it and rinsed it and put it in the tank but they float if there not under anything, is there a way I can get them to sink? Here are pictures:

 

For the light, I’d just get a cheap clip on one.

You also have some stocking issues, if you don’t mind me talking about them

 

Go ahead I would like to hear my problems how I can fix them and what I can do with my tank!

 

Ok.
Harlequin rasboras need at least a 15 gallon.
Neon tetras need a 20 long.
The betta isn’t temp compatable with the neons.
Cories need a 20 long.
Neons, cories, and harlequins need a school of at least 6.

If possible, upgrade to a 20 long, rehome the cories, and do this, assuming you have a good filter:
6-8 Harlequin rasboras
Your betta
6-8 bronze cories

 

On the wood, did you identify it and boil it?

 

On the wood, did you identify it and boil it?

Not sure of the type of wood. it came from some kind of vine I think, Yes I did boil it, for 5 minutes

Ok.
Harlequin rasboras need at least a 15 gallon.
Neon tetras need a 20 long.
The betta isn’t temp compatable with the neons.
Cories need a 20 long.
Neons, cories, and harlequins need a school of at least 6.

If possible, upgrade to a 20 long, rehome the cories, and do this, assuming you have a good filter:
6-8 Harlequin rasboras
Your betta
6-8 bronze cories

Okay thank you I will try to get one

 

Okay thank you I will try to get one

I’m glad to here it
Make sure you get a 20 gallon long, not a high! (As if I hadn’t said that enough in the previous post by me lol).
They have them at the dollar per gallon sale too, I think.

 

20 Long would be a good size and sand would be a great choice if you plan on keeping cories. You could do a 29 Gallon as well which is the same footprint as the 20 long, but about 6" taller. If you keep live plants, just keep in mind the extra distance for the lights to reach them in the 29.

You could also keep your Betta in the current 10 gallon and move everything else to a bigger tank if you don't mind having both running and have places for both.