Just tested my water

[Zoe Horsfield]

You're not 'going wrong', if you had high nitrate it might signal under-cleaning/ over-feeding but your nitrate looks under 20ppm which is where it should be.
The nitrite presence is a sign of an aquarium cycling which is when the beneficial bacteria develop.This is being monitored and water changed out.
If you increase your water changes and follow Byron's advise above you will maintain your water quality. This includes getting the 100 litre tank you are planning.
The pH, GH and KH are just what is in your tap and Deanasue and Byron have said goldfish do fine with this.
You are doing fine and you have a lovely fish!

Thank you I will try feeding him/her less, I was told by my local pets at home to only do a 20% water change once every 2 weeks so Do you think I should be doing it more frequently? And with the larger amount of water changed

 

[Naughts]

Thank you I will try feeding him/her less, I was told by my local pets at home to only do a 20% water change once every 2 weeks so Do you think I should be doing it more frequently? And with the larger amount of water changed

Yes, most people agree 50% per week is necessary. I'd go with Deanasue's recommendation, 75% per week. The pets at home advise isn't enough for any tank, you're tank is small and goldfish have a high bioload so you need to change a lot.

 

[Zoe Horsfield]

Yes, most people agree 50% per week is necessary. I'd go with Deanasue's recommendation, 75% per week. The pets at home advise isn't enough for any tank, you're tank is small and goldfish have a high bioload so you need to change a lot.

Thank you I’ll up my cleaning game and see if this makes a difference which I’m sure it will and I’m sure “Goldie” will thank me for it too

 

[Essjay]

Pets@Home has a very poor reputation for advice. I would ignore everything they say, to be honest.

 

[Zoe Horsfield]

Pets@Home has a very poor reputation for advice. I would ignore everything they say, to be honest.

I will absolutely give them a swerve next time I need any advice

 

[Jan Cavalieri]

And we all should keep in mind that not everybody can do a 75% water change due to the way their tank is shaped = for example long tanks can be difficult to remove 75% if you want your fish to have enough water to breath in. If it's important that it be at least 75% then tell them to put the fish in a bucket with an air stone going (I'm sure they'll be even more thrilled to do a water change). Also if you have 30 lbs of decorations offsetting the water in a medium size tank then you'll need to make an adjustment on what really is 50 or 75% of the WATER not the tank. Sometimes people have to be realistic about the advice they are getting or giving. And you know sometimes you do all those water changes and it just doesn't make a difference to your water numbers (that's the problem I'm currently having) Two have lost their cycle and just sit there with ammonium in them since they lack the bacteria to change it into nitrites (even when adding extra bottled bacteria) - this has been going on for over 3 months - no fish losses yet. Oh and never use brown substrate or you'll never be able to tell how much you may have overfed the fish. I bought the Sechem labeled "Dark" assuming they meant "grey" and it came out very very medium brown.

 

[Byron]

And we all should keep in mind that not everybody can do a 75% water change due to the way their tank is shaped = for example long tanks can be difficult to remove 75% if you want your fish to have enough water to breath in. If it's important that it be at least 75% then tell them to put the fish in a bucket with an air stone going (I'm sure they'll be even more thrilled to do a water change). Also if you have 30 lbs of decorations offsetting the water in a medium size tank then you'll need to make an adjustment on what really is 50 or 75% of the WATER not the tank. Sometimes people have to be realistic about the advice they are getting or giving. And you know sometimes you do all those water changes and it just doesn't make a difference to your water numbers (that's the problem I'm currently having) Two have lost their cycle and just sit there with ammonium in them since they lack the bacteria to change it into nitrites (even when adding extra bottled bacteria) - this has been going on for over 3 months - no fish losses yet.

It may help to clarify what most of us mean when we say 50-70% or whatever of the water should be changed once each week. This is the percentage of the actual water in the tank, not the percentage of what the tank holds when empty.

I tend to simply siphon out water down to below the half-way point on the tank. I've no idea how many gallons this could be, or even the percentage, for most tanks as I use the Python. But on the 10g it is very easy to over-fill the tank with the Python, so I use buckets. Each holds 2.5 gallons, and I use two full buckets to replace the water. So I know that is 5 gallons, but the tank obviously only has about 8 gallons of water taking into account the displacement by sand substrate and two chunks of wood. I siphon out water until the water level in the tank is below the half-way point. I would assume this ends up being about 60 or 65% of the actual volume.

In my 40g tank which is 12 inches high, and has about 1.5 inch depth of sand, I siphone out the water until there is about 4 inches of water left. I've no idea what percentage this is, but I know it is certainly 65% or more.

Significant water changes do impact the tank's biological significantly. The more water changed, the more stable the chemistry. Always assuming thee tank is biologically in balance to begin with. And the parameters (GH, KH, pH and temperature) are basically the same between tank water and tap water. Or if not, then preparing the fresh water outside the tank.

Ammonia along with any other pollutants will be reduced with a water change, unless it occurs in the tap water (ammonia from chloramine is one possibility). I am aware of the former threads on this ammonia issue, and it won't help to get into that here.