Whether the betta would work is kind of a moot point - that is not a well-stocked tank. Hatchetfish should be in schools of six, plecos get too big and produce too much waste to live in a ten gallon long term, and guppies are social fish, preferring to be in groups of three.
It might be a better idea for her to sort out the needs of her current fish, rather than adding another.
All that said, it's not a combination I would advise anyway. The betta may well bully the hatchet and the guppy.
The current state of stocking and tank situation is not a very good situation for any type if living creature, along with bettas to be placed in a tank of the one you have stated above. While there are a range, and varitety of Plecos. Very few are the best suited for a 10 gallon long, which are very uncommon in the aquarium trade. Assuming you have the most common ones referred as common or sailfin Plecos. You do have a potential problem regarding the adult size if the fish which is about 18-24 inches, bio load which could easily crash the cycle if the tank, and agression, as most Plecos get larger they will target smaller defenses fish in singles or pairs. So ideally you would want to rehome this fish.
Hatchet fish are quite stunning and exquisite aqurium fish in which Love to be in large schools of 10+ which any 10 gallon can't support properly, also many if the more common types are very active and have been known to slam into the aquarium walls when they are swimming, in a group if this size you annot support a proper school which would mean that you will not see this
Feeder guppies which are just wild guppies are another rewarding fish that are hardier than that if fancy guppies do to the strains of feeders where as fancies have been inbred for generations and generations. While these fish are a good tankmate for a female Betta they don't do well in small groups and are very social fish, I would recommend more so of getting 2 more females at the least.
When you have taken all these steps such as removing the Pleco, hatchet, and upping the numbers if gupies you then can think about adding the bettas
bluntness is needed to fully understand situations, where as I don't see the above post mean, rude or hurtful at all I can see situations to where as sensitive people might take it another way. When Someone can be rude or have a serious tone sounding a bit blunt, it makes me, not sure about you understand that this situation is very serious in lots of aspects
I know the breed of pleco she has is not a common pleco. We have 3 common plecos and none of them look like hers.
I knew there was something up with the hatchet fish. She had 3 of them at one point in time, but 2 jumped out and died.
Her guppies reproduce quickly. She only has the one female because as of the moment, it is fat and full of eggs. It will pop sometime in April and keep reproducing for several months, even without a male in sight.
I think that was my mom and sisters strategy when they didn't talk to the LFS and tell them what size her tank was...
I'll let her know though.
The biggest tank we have is a 75 gallon, but it has 2 huge plecos, a tiger oscar, and all of her previous guppies (which the oscar cannot see, therefor, he cannot eat them)
I'm pretty sure the hatchet fishes would be eaten within a day of being placed in the tank.
Theres also my 25/30 gallon(not sure which one yet), but it too has a pleco, as well as 5 female bettas and 3 cory cats...
My pleco is only as big as his tank and tends to poop a lot( as mentioned. Praise the lord for monthly tank siphoning! lol!)
Before adding more hatchets I have a slight concern.. Two jumped out?
They may not look it, but they are very good jumpers, can jump like six inches out of the water, and even glide a bit. Hatchets need very secure lids, as they are crazy little buggers :)
Yes. Hatchets Ideally should be provided with a somewhat large tank as they are quite active fish. They have been extremely well known to injure themselves in ornaments, along with jumping out if the tank. One of the most likely resons to as why your hatchets aren't ehxibitng this behavior could likely be due to the School size. They should be in schools in no less than six, ideally 10 as by keeping smaller could put them in danger leaving them very succeptable to diseases, getting picked on, being nippy, and feeling insecure. I would highly recommend that you rehome this species along with the pleco unless it is a pitbull, bushy nose, bristlenose or bull dog plecos. Then you can ideally keep then in a 20 gallon tank, provided lots of filterstion and a mature, cycled tank with stable water parameters
Also, what types of hatchets do you have. As most of the more common species such as marble, pygmy and silvers are all a bad choice for your tank IMO