However, I think the number one suggestion for your particular situation, since it's not your fish, would be ask the owner. I'm surprised no-one suggested that already. They'll know what they want to do with their pet and are best placed to answer your query. In practice, it would have been better to ask the owner before they went away. A short conversation along the lines of "What should I do if one of them dies?" would better prepare you if you have to deal with this sort of thing again.
Cory cats and neon tetras make great first fish
Stay away from vet food. Vet clinic recommend their crap because they get kick backs.
Wysong Epigen Starch free; been there done that…makes for soft or loose stool…got tired of cleaning my dog’s rear end.
Best kibbles on the market today is Orijen: first 5 ingredients are meat, then low glycemic fruits and veggies and basically no carbs.
Second, with first 3 ingredients being pure meat, then low carbs, low glycemic organic veggies and fruits is Natural Planet rabbit/salmon or duck/white fish.
Best dog food overall is freeze dried Stella’s & Chewy almost all meat and starch free.
One MUST switch food at least every year to prevent intolerance to some ingredients. The only kibbles that should be fed to pets must have pure meat as the first 3 ingredients listed.
DO NOT feed potatoes base food. Starch, carbs are sugar and create yeast overgrowth making pets very itchy.
Run of the mill vets put every itchy dogs in the same label and prescribe armful allergy meds.
Yes, premium pet food is expensive but will save you trips to the vet in the long run.
Same goes for treats.
Community Tank: Housing Multiple Fish Together | PetSmart
Guppies are incredibly easy to keep alive. Just keep the tank clean and provide them with food (they’ll eat just about anything and are great for mosquito control), and . There are a few diseases they can catch, such as fungus infections, but if you start with a healthy stock of fish, you can potentially avoid the problem. To get healthy fish at the start, it’s best to buy them from pet stores that source from local breeders, rather than imported fish, since they have been less stressed in transportation and have adjusted to life in an aquarium rather than a hatchery.
These fish aren't as aggressive as African cichlids