I'm on the fence here. I am often left to run a 140 tank store on my own these days, and I can see things from the sales staffs' point of view. Even when I get more staff, it's on a busy day so we can't do maintanance, hence I have to do it myself during the weekdays on which I'm in..... Then again, I also visuit many shops in my local area fairly regularly and still see things from a customer's prospective also.
Angels and tetras can work long-term. Put the tetras with your angels while the angels are small and they are usualy OK, as the angels don't associate them as food. Get but angels in, and then add tetras and you'll then get your problems. Angels are used to you opening the tank and adding food, so when you open up and add snack-size neons, the food assosiation is regained and the angels have a nice slap-up meal... The adult angels associate anyting small and moving with food when first introduced, explaining those issues, but when you raise them with the tetras, they don't usualy bother them, as they couldn't eat them when first introduced and thus don't see them as food.
As both the above posters say, Fighters have different personalities. Most IME are fine with Neons, but you do get the odd one. Yes, idealy this fish would be moved, but in a busy retail enironment, the staff may just have been called away everytime that they tried to get round to it... Yes, to a customer it does not look good, but the staff may not be able to get round to it quickly, if there weren't enough staff on that day to deal with maintanance jobs and serving... In retail on your own, you also have to prioritise the jobs that need doing. Which would get periorty with you, the tank with the bust filter that is currently going over, or the tank with a single lone fighter picking on neons? To me, it would the the crashing tank first everytime...
You will need to realy look at how the store runs before drawing conclusions about the staff and the store. If there were more than enough staff on and they were not that busy, then they should have seen it. I'd have pointed it out, as they may not have seen it, after all they have to watch many tanks as well as serving and maintaning, they cannot see everything. If they ignored it once it was pinted out, they I'd have then made judgements about that staff member...
"Take and go" tanks are a new one on me. They sound like a cheat, but a workable cheat all the same to me, and I would not worry too much about that individual issue, as there are far worse things that they could sell, like Goldfish bowls, that I blatently don't agree with. If I had my way, my place of work would not still be offering them, but belive it or not, there is more money in those that the lage package tank deals, where the prices have been driven so low that costs are barely covered by them... This is why even reputable stores are reluctant to let them go, as they have to ballence the books at the end of the day
All the best
Rabbut