2 guppies are missing parts of their tails.

[emeraldking]

or use a sponge filter..

Unless that one is also made of carbon. There are also blue sponge filters that are better while using meds.

Will the tetras attack the fins? What tetras? What species is important to say. Some nip, some don't.

True...

I just lost 2 more guppy fish

So, sorry to hear...

but the guppies probably feel like they were swimming dragging a wedding dress, and now, it's gone. They are probably delighted.

I have to agree with this...

 

[Essjay]

What tetras?

Glo-skirt tetras, which are known fin nippers.

 

[pettygil]

My betta is doing fine in his own home. My tetras are doing fine. It's the guppies that keep dying. No worries, I do not plan on buying anymore guppies. I am doing plenty of water changes. I always check my water. I do not think with my water I can keep Guppies. Also I do not want my tank over crowded.

 

[pettygil]

I only have 3 guppies in my 20 gallon, the rest of the guppies I had, died.

 

[pettygil]

If my guppies live, which I have 3 guppies, can I put 3 guppies in a 6.5 gallon tank,, setup? or do a ten gallon and if so, how many guppies ,for 10 gallon?

 

[kiko]

you can check different tank sizes and different fish with a stocking calculator
you can find one at: https://aqadvisor.com/

 

[pettygil]

you can check different tank sizes and different fish with a stocking calculator
you can find one at: https://aqadvisor.com/

It says

• Suggestion: If you want to keep more than 1 Guppy, minimum recommend male to female ratio is 1:2 (M:F). You will be less likely to experience problem if you get even more females.
• Warning: At least 5 x Red Eye Tetra are recommended in a group.
• Warning: Red Eye Tetra will likely to fin nip Guppy.

Recommended temperature range: 75.2 - 78.8 F. [Display in Celsius]
Recommended pH range: 5.5 - 7.5.
Recommended hardness range: 1 - 15 dH.

You have plenty of aquarium filtration capacity.

Your aquarium filtration capacity for above selected species is 184%.
Recommended water change schedule: 21% per week.
Your aquarium stocking level is 78%.

 

[Essjay]

No stocking calculator is perfect.

At least 5 x Red Eye Tetra are recommended in a group.

We now know that shoaling fish do better in groups of at least 10, and this is particularly important with fin nippers like red eyes in the hope that they'll keep their nippiness within the group. Even so, fish with long tails will be too tempting for nippy fish to resist.

While that guppy male/female ratio is OK, it doesn't say you can have all males or all females if you wish.

At 78% stocked, I would do more like 50% water changes per week.

 

[pettygil]

No stocking calculator is perfect.

We now know that shoaling fish do better in groups of at least 10, and this is particularly important with fin nippers like red eyes in the hope that they'll keep their nippiness within the group. Even so, fish with long tails will be too tempting for nippy fish to resist.

While that guppy male/female ratio is OK, it doesn't say you can have all males or all females if you wish.

At 78% stocked, I would do more like 50% water changes per week.

I will do 50 percent weekly water changes to my 20 gallon. I have to do wc everyday with my Betta, because the 3 gallon is not cycled, yet. I'm going to have to buy 3 more red eyed tetra for my 20 gallon tank. That would make a total of 6 red eyed tetra. I'm buying a 10 gallon tank for my 3 guppies. I'm going to buy all male guppy fish. I do not want any fry fishes. I meat to say 3 guppies, not betta's. sorry bout that.

 

[Byron]

I will do 50 percent weekly water changes to my 20 gallon. I have to do wc everyday with my Betta, because the 3 gallon is not cycled, yet. I'm going to have to buy 3 more red eyed tetra for my 20 gallon tank. That would make a total of 6 red eyed tetra. I'm buying a 10 gallon tank for my 3 guppies. I'm going to buy all male guppy fish. I do not want any fry fishes. I meat to say 3 guppies, not betta's. sorry bout that.

Following up on what @Essjay wisely advised, I do not consider a 20g suitable space for red eye tetras. You need a group of 10 (or more), and this is an active swimmer so it needs space. Fewer will inevitably be problematic.

Aquadvisor is a very basic guide but no where near reliable. There are a lot of issues factoring in to stocking an aquarium, and no automated programme can include all of them, it takes human thought.