Please Help With My Fish Tank Community Question

And this

I meant this one

One dead new fish out of six is not uncommon. If you mean a second one has died, that is less common.

There is always the possibility they were sick when you got them. Fish are very good at hiding the fact they aren't well as that makes them easier for predators to pick off, and other members of the shoal will also likely pick on sick fish so they don't attract predators to the shoal. So it is in a fish's interest to look fit and healthy right up to that last minute.

Did the dead fish show any symptoms eg white spots or botches, disintegrating fins, bloated body, bloody streaks on the fins or body? Though a fish that has been dead a while may have been partially eaten by its tank mates.

Nitrite should be 0 - anything above that is toxic to the fish. It's normal to have some nitrate - usually 20ppm although many folk have trouble keeping it under 40ppm due to their tapwater having high levels. What do you get for nitrate when you test the water straight from the tap?

That is a good nitrate level for tap water. The UK allows up to 50 ppm, and a lot of people have almost that level in their tap water.

Nitrate in an aquarium should be kept as low as possible, and with your tapwater level, you should aim to keep it below the 20 ppm that fcmf said.
Nitrate is the end product of the nitrogen cycle. Fish excrete ammonia, one set of bacteria turn that ammonia into nitrite; another set of bacteria turn that nitrite into nitrate. In fish tanks, there are no bacteria to remove nitrate, though plants do use it (and ammonia) as fertiliser. This is one reason we do water changes, to remove nitrate and other things like hormones secreted by the fish.
When a tank is fully stocked, nitrate should go up between water changes by no more than 20 ppm, and since your tap water is virtually zero, that means the maximum it should go up between water changes is from 0 to 20. My tanks are fully stocked, and nitrate doesn't increase by that much.
Because your tank is lightly stocked at the moment, the fish you have won't make much ammonia for the tank size, so you won't get much nitrate. As you get more fish and your stocking level reaches the maximum, you should see some nitrate at the end of the week just before a water change.

Blimey serious grats on the zero nitrates, I'm well jel 

And to think I get pulled up for the odd grammar error..... at least I speak recognisable words!

Having a bit of a crisis with the harlequins 4 in total have died but my water levels are still all at 0.
I have found my missing shrimp he randomly appeared again and all of my cherry barbs are fine it's getting to the point where I'm finding 1 dead harlequin a day so please help

Generally lead that is used to weight plants down should be removed so I wouldn't use it in a tank. I hope you don't mean you have the air pump inside the tank, just the air stone or some such 

If the cherry barbs are OK I would suggest a batch of sickly harlequins. Did you get the barbs from the same shop? if you did, what were the harlequins like in the shop tank? If they were from a different shop maybe go back and see if the shop's harlies are OK.
And as the shrimps are OK there is nothing wrong with your tank. Shrimps are more sensitive to iffy water than fish are.

Really upset to hear of your troubles Jack, it must be really disheartening for you. As Sue suggests you may have a sick batch of harlequins... Chances are they wouldn't have been in pets at home very long, I believe they have a quick turnaround of stock. I do wonder what they do with unsold stock???

I honestly thinking that if they all die I'm not bothering with them again I will just stick to the barbs as they seem to be fine but the only thing is there not shoal ingredients they just stick to groups of two