Thanks so much for your reply! I hope he’s not upset because I cut the plants back, they had taken over the whole tank and you couldn’t really see the fish anymore!
It's fine to trim the plants back, we have to now and again, and it's great they're growing that fast! But worth leaving at least some large leaved plant stems closer to the surface for a betta, they love to rest on leaves, or artificial decor like betta hammocks since they like to use them to rest on, and they're labyrinth fish so can breathe from the surface, and having some nice dense plants or some broad leaves to lie on while on the bottom, and to rest on near the surface, is good for bettas. Especially ones with long heavy fins, those cause a lot of drag in the water, and they're not super strong swimmers, so they appreciate the comfy resting spots!
I’ve turned the temp up a degree (I got the original temp from a website) and I can return the guppies to the aquarium shop (the sales person there said it’s a good combo) but they very rarely seem to take any notice of each other and I’ve never seen the betta flare.
I wouldn't return the Endler's at this point. While bettas are a solitary species and better off alone than in community tanks, do need softer water while Endler's need hard, and long term, that stocking might need reconsidered - it's not the Endler's causing this. Large tailed male guppies especially can sometimes trigger stress and aggression in a much more territorial and aggressive male, but Endler's don't have the giant tails and are much faster, and definitely aren't causing lethargy, excess mucus, and lack of appetite in the betta.
It's much more likely to be water conditions, illness or infection of some kind.
However, if you're willing to return fish, please, please return the juli corydora. Cories are a very social species, need groups of at least six, and need sand, not a gravel substrate. Getting more of them right now when there might be sickness in the tank is a bad idea, and would face the same issues of the gravel substrate, and we really need to find out some more info about your general water parameters, like whether your water is hard or soft, before we can recommend better stocking. But the cory will be lonely and stressed without other cories, so you'd be doing a kindness in returning him, then working with us to learn more about your set up and more compatable stocking, before adding more fish.
Hopefully the betta can recover and pull through! We definitely want to try to help! Sadly as you're learning the hard way, fish store employees often give terrible advice! Especially the big box chain stores. Many of us learned the hard way that they will often sell snake oil products, give inaccurate info that kills fish and puts people off the hobby, or sell sick, unhealthy fish to people who don't know any better yet, and put them off the hobby altogether. Not all store employees of course, not all stores - some are amazing! But when you're new to the hobby, it's easy to trust their advice, then get burned. Always do your own research, and be wary of advice from a store!
Another reason to return the cory while keeping the Endler's is that we don't know yet whether your water is hard or soft. Majority of fish in the hobby, and the betta and Juli cories - need softer water, while Endler's and other livebearers need hard water. If yours turns out to be hard, and the betta passes, you'd be left with a single, stressed and lonely cory on the wrong substrate.
So my current suggestion is to fill out as much info as you can, return the cory to the store, and take a water sample with you. Ask them to please test it for ammonia, nitrites, and nitrAtes, and also if they can test the GH and KH for you. Ask them to write down the numbers for these, not just say that they're "fine", we need to know the actual numbers in order to know what's going on in the tank, what kind of water parameters you have, and so whether something in the water is affecting the betta, and which sorts of fish would work best in your water.
I have noticed his colours have changed, he’s become less vibrant. Here’s some more photos if it helps.
He’s eating very little now and doesn’t swim over to say hi when I look in on him anymore.
