New to this!

[Birmingham Transport]

Hi, got my 1st Aquarium at the tender age of 46! It’s a 190 litre Juwel Trigon. Introduced 6 Cardinal Tetras yesterday, however the smallest one has been hiding away on his own in the top corner of the tank. He doesn’t appear to be distressed in any way but just then he dropped to the bottom of the tank and lay upside down. Now I’m no fish expert but I’m sure that’s not good!! After a couple of minutes he’s ok swimming back to the top again. I would be grateful for any guidance. Thank you

 

[KevinZ]

, hello
If you just got your aquarium from 1 August then probably they got Ammonia burn / Stress Do you aware of cycling Process?
You can read it here.

Cycle your Tank

Cycling a tank is vital to keeping your fish alive. This section is where you can read about cycling (the nitrogen cycle) and ask questions about how to do it properly.

www.fishforums.net

 

[PhantomCarp]

Welcome to the TTF community and to the hobby

 

[Birmingham Transport]

, hello
If you just got your aquarium from 1 August then probably they got Ammonia burn / Stress Do you aware of cycling Process?
You can read it here.

Cycle your Tank

Cycling a tank is vital to keeping your fish alive. This section is where you can read about cycling (the nitrogen cycle) and ask questions about how to do it properly.

www.fishforums.net

I’ve had it about 3 weeks now, these are the 1st fish to be introduced. I took a water sample to Pets at Home before they’d sell me the fish.

 

[FishFinatic77]

Welcome to TFF!
I agree with @KevinZ, your aquarium is not cycled. Since you already have fish in the tank, you'll have to do a fish in cycle. I would do a 75% water change for now, and then test your water for any ammonia, and nitrites. (You're not going to have any nitrates yet.) Test your water every day to you see if you have any ammonia or nitrites in the water. If you do, then do a 50% water change. After about 3 weeks, you can start testing for nitrates. Your goal is to constantly have 0 ppm ammonia, 0 ppm nitrites, and 0-20 ppm nitrates.
Do not replace the filter cartridge during this process. You're trying to get beneficial bacteria to grow in the filter, and replacing the cartridge will set your cycle back.
Also, do you have your own test kit? If not, I would get one. You're going to need it for this. The API liquid test kit is the best one. Try to avoid the strips as they aren't always acurate and they don't test for ammonia.

 

[FishFinatic77]

I’ve had it about 3 weeks now, these are the 1st fish to be introduced. I took a water sample to Pets at Home before they’d sell me the fish.

If you're starting a cycle from scratch (so you're not using any started media), then it can take 2 months to cycle your tank.
You were told that your water was fine because you didn't have any source of ammonia in the tank to get the cycle going. Running the tank for 3 weeks does absolutely nothing.
Also, the people in places like Pets at Home, Petco, and Petsmart tend have no idea what they're doing. Don't ask them for any advice. You'll just get yourself into a big mess. Most of us here have had to learn that the hard way.

 

[Birmingham Transport]

Welcome to TFF!
I agree with @KevinZ, your aquarium is not cycled. Since you already have fish in the tank, you'll have to do a fish in cycle. I would do a 75% water change for now, and then test your water for any ammonia, and nitrites. (You're not going to have any nitrates yet.) Test your water every day to you see if you have any ammonia or nitrites in the water. If you do, then do a 50% water change. After about 3 weeks, you can start testing for nitrates. Your goal is to constantly have 0 ppm ammonia, 0 ppm nitrites, and 0-20 ppm nitrates.
Do not replace the filter cartridge during this process. You're trying to get beneficial bacteria to grow in the filter, and replacing the cartridge will set your cycle back.
Also, do you have your own test kit? If not, I would get one. You're going to need it for this. The API liquid test kit is the best one. Try to avoid the strips as they aren't always acurate and they don't test for ammonia.

Thank you. Will do the above. I only have the testing strips so will get the liquid one instead. Thanks for a speedy reply!

 

[Salty&Onion]

I’ve had it about 3 weeks now, these are the 1st fish to be introduced. I took a water sample to Pets at Home before they’d sell me the fish.

Cycle takes up to 6 weeks, you have been misguided by them as they just want to make a sale as fast as possible.
I would not recommend buying from pets at home as thye have disease ridden fish and tanks, I have lost too many fish from them and have sworn that I will never again buy fish from them.
I would recommend buying fish from Maidenhead Aquatics as they are more experienced in fish and stocking, at least my local one does IMO.
Neon tetras, tetras in general, are soft water fish species and they require soft water and acidic pH.
Can you provide us with your pH, GH and KH?
KH is the carbonate hardness while GH is the permanent one and these minerals can be removed by reverse osmosis system, @Retired Viking uses this system for his tetras and therefore is more experienced.
I'm also aware that Maidenhead Aquatics sells RO water for cheap, but you do have to have your own containers.
When you get the RO water from them, use half of it and half of your tap water mix so the water has still some minerals the fish could use, but there will be no residue buildup in their kidneys.
They will also require floating plants as they come from amazonian river/s wich has some shades and low light.
As for your main water parameters, ammonia and nitrite in cycled tanks should be 0ppm for both. Nitrates should be kept below 20ppm.
What is your ammonia, nitrite and nitrates?

 

[FishGuest5123]

Cycle takes up to 6 weeks, you have been misguided by them as they just want to make a sale as fast as possible.
I would not recommend buying from pets at home as thye have disease ridden fish and tanks, I have lost too many fish from them and have sworn that I will never again buy fish from them.
I would recommend buying fish from Maidenhead Aquatics as they are more experienced in fish and stocking, at least my local one does IMO.
Neon tetras, tetras in general, are soft water fish species and they require soft water and acidic pH.
Can you provide us with your pH, GH and KH?
KH is the carbonate hardness while GH is the permanent one and these minerals can be removed by reverse osmosis system, @Retired Viking uses this system for his tetras and therefore is more experienced.
I'm also aware that Maidenhead Aquatics sells RO water for cheap, but you do have to have your own containers.
When you get the RO water from them, use half of it and half of your tap water mix so the water has still some minerals the fish could use, but there will be no residue buildup in their kidneys.
They will also require floating plants as they come from amazonian river/s wich has some shades and low light.
As for your main water parameters, ammonia and nitrite in cycled tanks should be 0ppm for both. Nitrates should be kept below 20ppm.
What is your ammonia, nitrite and nitrates?

I think we need to get OP’s tank cycled with as little confusion as possible. Read the article given above to better understand the Nitrogen Cycle. Then buy some Tetra Safe Start + to help get the bacteria growing. If you use Seachem Prime, don’t for 24 hours after adding Safe Start. Then it is wise to use it as your dechlorinator as it will detoxify ammonia, nitrites, and nitrates for 24 hours. Here if you need us.

 

[Essjay]

The first part of this https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/ explains what cycling is. You can ignore the second part as that is for cycling before you have fish.

 

[Retired Viking]

I agree with @Deanasue about using Tetra Safe Start Plus to help jump start your cycle, if you can not find it Dr. Tim's Aquatics also works and may be easier to find in the UK.

 

[Essjay]

It's the other way round @Retired Viking - Tetra Safe Start is widely available but Dr Tim's is hard to come by. There's just one seller on Ebay and Amazon market place (same seller) that I can find for Dr Tim's.