Im a little confused here, I thought the paradise fish had been in a while and weren't causing any problems?

He already traded it all for two lady betta fish.

How are they getting on nathan?

Its kind of hard to guess whats wrong when there are no specific symptoms. Have you noticed any stunting, yellowing, brown spots, pinholes etc?

Just general slow growth in my tank usually means Ive let the floating plants take over and there isn't enough light, the bulbs need changing or I've under dosed nitrates again. Could you give your most recent test results? Maybe something will jump out.

looks like a little bit of algae, nothing scary but it may become a little unsightly. It should sort itself out over time.

PAH do actually provide training and want their staff to be able advise customers. Unfortunately what they teach doesn't even broadly tally with the advice you will get from a good online community.

2 paradise fish - very aggressive, questionable community fish. Should not be kept together in a small tank, even a male/female pair needs about 90l and lots of hiding places.

2 swordtails - hardwater fish

2 peppered Corey's - soft water fish, should be kept in a shoal of 6+

6 neon tetras - soft water fish

Thats just what I've noticed at first glance. I suspect your shop hasn't been giving the best advice.

Bit of an odd mix there, what size tank do you have and what water hardness and PH?

Shops have a high turnover of animals and corals so you never know what hitchhikers they have brought in so I doubt its worth the risk. Thats assuming you find a shop that would be willing to help you. A large part of fishkeeping is about patience and research. The set up is all part of the fun and will give you time to get to grips with maintenance. I expect you will have your hands full anyway with learning to keep such a small tank stable.

This forum is almost exclusively freshwater so you will need to do more research elsewhere but here are a few pointers:

Be wary of following the tank instructions without doing your own research. While it does tally with that I know about marine I'm not an expert. You may find that the manufacturers way of doing things is not always the best way. They are suggesting that you use live rock, sand and water from another tank that you already have running when they suggest using 'mature water'. If you don't already have a marine tank you most likely cant get those things and need to cycle the tank yourself. They have instructions for that on page 8. 'Prepared seawater' will be RO filtered water from an aquatics shop and marine salt and the next page is actually a guide in how to make/use it.

GL with your marine adventure :)

Its probably a mixture of issues but the tank size and possible water quality ones can be fixed. You cant do anything about poisoning.

To give them the best chance short term keep up partial water changes of about 50% a day and buy them a large foodsafe box to live in. Asda and Staples do good ones that are 100 liters+ and they don't cost a lot. Fish do not do well with sudden changes to their water so you will need to bag them up and acclimatise them to the new 'tank' by floating the bag in the box and slowly adding more new water to the bag over the space of an hour. The you can tip the bag and let them swim free.

GL, I hope they make it.