Measurements for a newbie

Cuileann · Oct 4, 2021

I am very new to the hobby and we have bought the Tetra 105l starter kit. We plan to cycle it and move the fish we rescued into it. (they were going to get flushed down the toilet) It advertises as 105l. (H48cm, W76cm, D37cm)

I used a calculator here and with the measurements it says it holds 135l not 105l. I know when adding things like water conditioner or treatments, you have to be accurate.

Can anyone help? And when using most treatments it is in gallons not litres but never specifies US or Imperial.

What gallons would you recommend I use?

Thank you so much in advance. I hope this is the right place to ask these kind of things. If not, I apologise.

Bruce Leyland-Jones · Oct 4, 2021

...And then you've got the volume taken up by substrate, rocks, wood, etc..

I suggest you do what I did when first filling the tank;
I placed the substrate, rocks and wood in and then added water from an 8 litre bucket.
I filled the tank to halfway-ish and made a note of how many buckets I'd used.
At that point, I added the plants and then continued to fill the tank.
By the end of it, I knew that my tank held 101 litres.

The Gallon/Imperial Gallon thing is one to watch out for, especially as there's a significant difference and difference measurements are favoured in different forums. For this reason, I use litres and litres only.

Myraan · Oct 4, 2021

Usually the actually capacity is less than that advertised because of what you say.

If I had to guess in this case though, I think the person doing the write-up for the online seller made a booboo and wrote 48cm height instead of 40cm.

Cuileann · Oct 4, 2021

Bruce Leyland-Jones said:
...And then you've got the volume taken up by substrate, rocks, wood, etc..

I suggest you do what I did when first filling the tank;
I placed the substrate, rocks and wood in and then added water from an 8 litre bucket.
I filled the tank to halfway-ish and made a note of how many buckets I'd used.
At that point, I added the plants and then continued to fill the tank.
By the end of it, I knew that my tank held 101 litres.

The Gallon/Imperial Gallon thing is one to watch out for, especially as there's a significant difference and difference measurements are favoured in different forums. For this reason, I use litres and litres only.

Thank you, I have a 6 litre bucket to keep an eye out.
I am in Scotland so we use litres. My only problem is I notice things like Seachem Prime which I plan to use, is gallons as is a few things I have encountered. And with them, I am not sure how to properly convert the gallons to litres.

Essjay · Oct 4, 2021

The dimensions include the lid so the height is a lot taller than the actual tank. From Tetra's website (my bold highlighting)

Aquarium dimensions including lid (WxHxD): 76 x 48 x 37 cm

Sellers will use those dimensions but omit the fact that the height includes the lid.

The safest way, as Bruce said, is to measure the amount of water you put in when you fill it up.
Water conditioner is best used by adding it to a bucket of water before it is put in the tank, at the dose rate for the amount of water in the bucket. Buckets with graduations marked inside them are very useful.

I've only ever come across one brand which uses imperial gallons and that's King British. All others use American gallons. Litres are far safer.

Essjay · Oct 4, 2021

Cuileann said:
I am not sure how to properly convert the gallons to litres.

Use the calculator on here - and it's American gallons as Seachem is an American company

Cuileann · Oct 4, 2021

Myraan said:
Usually the actually capacity is less than that advertised because of what you say.

If I had to guess in this case though, I think the person doing the write-up for the online seller made a booboo and wrote 48cm height instead of 40cm.

I will make sure to accurately measure the height when I receive it tonight. I assume that will only need to cover the tank and not the top lid included.

It just seems like a huge leap from 105l (advertised) to 135l (measured through the site’s converter.) That’s what is really confusing me.

Cuileann · Oct 4, 2021

Essjay said:
The dimensions include the lid so the height is a lot taller than the actual tank. From Tetra's website (my bold highlighting)

Sellers will use those dimensions but omit the fact that the height includes the lid.

The safest way, as Bruce said, is to measure the amount of water you put in when you fill it up.
Water conditioner is best used by adding it to a bucket of water before it is put in the tank, at the dose rate for the amount of water in the bucket. Buckets with graduations marked inside them are very useful.

I've only ever come across one brand which uses imperial gallons and that's King British. All others use American gallons. Litres are far safer.

Thank you so much for the info. So I will measure not including the lid and keep an eye on my bucket amounts.

The litres and US gallons info was also so useful.

Cuileann · Oct 4, 2021

Essjay said:
Use the calculator on here - and it's American gallons as Seachem is an American company

Brilliant. That will do the trick

Colin_T · Oct 5, 2021

To work out the volume of water in the tank:
measure length x width x height in cm.
divide by 1000.
= volume in litres.

If you have big rocks or driftwood in the tank, remove these so you get a more accurate water volume.

When you measure the height, measure from the top of the substrate to the top of the water level.

You can use a permanent marker to draw a line on the tank at the water level and put down how many litres are in the tank at that level.

There is a calculator/ converter in the "FishForum.net Calculator" under "Useful Links" at the bottom of this page that will let you convert litres to gallons if you need it.

Bruce Leyland-Jones · Oct 5, 2021

Colin_T said:
If you have big rocks or driftwood in the tank, remove these so you get a more accurate water volume.

Surely, if you do this, you'll only get the volume for an empty tank and I'll assume that the tank won't be empty for long.
Any volume calculation gained by doing this will become invalid, as soon as you add the wood and rocks.

I still say that it's best to measure the water you put in, once the hard landscaping has been added. This then tells you how much water is really in the tank and this volume will be the most accurate for when it comes to measuring conditioners, medications, etc. and calculating stocking levels.

Colin_T · Oct 6, 2021

Colin_T said:
If you have big rocks or driftwood in the tank, remove these so you get a more accurate water volume.

Bruce Leyland-Jones said:
Surely, if you do this, you'll only get the volume for an empty tank and I'll assume that the tank won't be empty for long.
Any volume calculation gained by doing this will become invalid, as soon as you add the wood and rocks.

Removing the big rocks and big bits of driftwood will not remove the water. Likewise putting them back in won't change the amount of water in the tank. You don't remove the gravel or plants. You simply measure from the top of the gravel to the top of the water level. After you have measured that you can put the rocks and wood back into the tank.

Removing these items means you get a more accurate volume in the tank because the large items are not displacing water. That means the water level in the tank will be lower without the items in and higher with the items in the tank.

Bruce Leyland-Jones · Oct 7, 2021

Colin_T said:
Removing the big rocks and big bits of driftwood will not remove the water. Likewise putting them back in won't change the amount of water in the tank. You don't remove the gravel or plants. You simply measure from the top of the gravel to the top of the water level. After you have measured that you can put the rocks and wood back into the tank.

Removing these items means you get a more accurate volume in the tank because the large items are not displacing water. That means the water level in the tank will be lower without the items in and higher with the items in the tank.

Again, all you are doing is measuring the capacity of the tank and not the amount of water you'll have to be working with, day in, day out.
The internal volume of the tank reduces when you put things in it and, whilst we can tentatively ignore the mass of fish and plants, ignoring the volume taken up my hard landscaping would be foolish.

Again, when setting up a tank, the absolute simplest method is to to measure the amount of water you put into it, after you've added substrate and rocks, etc..

Essjay · Oct 7, 2021

I get what Colin means. If there's no decor in the tank, you measure the width and length then the height from the top of the substrate to the water surface. That gives the volume of water. Then when the decor is put in, the water surface goes higher but the amount of water stays the same.

Question - when measuring width and length, is it usual to measure from the outside edge of the glass or the inside edge? My main tank is made from 10 mm glass so the outside measurements are 2 cm (almost an inch) more than the inside measurements. That alone makes a difference of 12 litres for my tank.

itiwhetu · Oct 7, 2021

Inside of the tank. The only accurate way of measuring volume in your tank is put all your substrate and decorations into the tank and then do what Bruce says measure the water you put into the tank. If you ever put another large rock in it will change the volume. This is most important when determining how much Dechlorinator you are adding, or any Fertilizer or medications. Your actual tank volume is vital to all things that you do with your tank.

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Measurements for a newbie

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