How much water do you really have in your tank? HINT: it's not what you think.

[najer]

Mine is a custom and the glass volume including sump is 700 litres, 550 litres of water went in when it was filled but more rock has been added.
I can only think medicating in tank is when you need to know, I had a damaged convict tang and medicated, the bottle said it treats 450 litres and I must be around 500 litres now so just dumped the whole bottle in.

 

[X-37B]

My 120 holds about 108 with inside dims.
My 40 breeder running at 6.5" is 17 gallons.
125 gal total without rock and equipment.
I have 75lbs rock plus corals.
I just go with 120 gal as its close enough for me and its probably closer to 110.
I Dont think it matters that much as long as your close for dosing things.
I always start low with any form of dosing anyway.

 

[Kscope]

Any way of calculating how much water our tanks really hold? Formulas?

Measure water in inches H/12×W/12×L/12 will give you water in cubic feet. Multiply that by 7.48 gallons per cubic foot

 

[Art2249]

I estimated the volume when I first set up the tank based on how much salt mix I used. I was using blue bucket red sea at that time and it took exactly 1/2 cup to make 1 gallon. So I used 80 cups and figured it at 160 gallons. it's pretty accurate based on brs calculator when i need to adjust something.

 

[CavalierReef]

I know what my water volume is because I added rock and sand and then measured the water that went in. Easy with a small tank not so much with a larger one I'm sure. I'm a lot more comfortable adding anything into my tank that has a recommended ratio because I know my water volume.

 

[krash7172]

I voted very important. It was very useful when determining my maintenance routine. Now that I have a stable mature tank and a set routine, it isn't as important. I have a 180 with a 120 sump. I estimated my total volume is around 200 gallons.

 

[Dburr1014]

I vote as somewhat important. If your dosing you should also be testing. That will make up the difference of actual and guess of how much water you have to add the proper dose. I will always under dose first, test, then finish dose.
Water changes still, % is close enough.

 

[725196]

1. How much water volume do you think you actually have in your main display and what was the manufacturers advertised gallons or liters?

When I first started my current tank I measured the inside measurements and also did a water displacement test on my rock. I added the sump volume to the point I would have water. My system had about 55 gallons of water. Since then it has gone down with the addition on corals,fish, atc

2. How important is it to have an accurate measurement of water volume in your system?

I think it is very important to k no is as close as you can to the volume amount. With this knowledge it helped with dosing and It should help understand water quality as well. I am under the firm belief that to be successful you keep good water and let everything else take care of itselF.

 

[mucky1957]

I might be wrong and if I am pls tell me. I was alway told that each kg of rock equaled a lt of water. So with that in mind..my tank is a 240lt tank and I knoe I have 50kg of rock in it..so therefore I work on the basis that my tank actually holds about 190lt of water.

 

[pdiehm]

Knowing the amount of water you actually have in your aquarium is pretty important considering it can impact quite a few areas of reef keeping. But it's not as easy as knowing the amount of gallons or liters the aquarium manufacturer says that your tank will hold. How much of the "liquid" space is taken up by your live rock and sand? How close to the top edge does the water need to be? What about your sump and the equipment in it? The plumbing etc. etc. etc? How important is it really? Let's talk about it.

Did you know that tank manufacturers measure the outside of the glass when calculating tank volume when the inside of the glass gives a more accurate measurement?

1. How much water volume do you think you actually have in your main display and what was the manufacturers advertised gallons or liters?

2. How important is it to have an accurate measurement of water volume in your system?

image via @Triton USA

it's important, but at the same time it's not. Being close isn't necessarily going to have an effect on things. For example in my 120, if i include the tank and sump, it's approximately 123.5 gallons. I round up to 125 because it's easier, and the test kits I have available to myself aren't going to pick up the difference in anything base on 123.5 vs 125.

I think being reasonably close (within 5%) suffices.

 

[dbowman5]

I might be wrong and if I am pls tell me. I was alway told that each kg of rock equaled a lt of water. So with that in mind..my tank is a 240lt tank and I knoe I have 50kg of rock in it..so therefore I work on the basis that my tank actually holds about 190lt of water.

a kg of water equals a liter of water but rock is heavier than water so it displaces less volume. my answer above references that. concrete is lighter than granite but still sinks in water.

 

[blasterman]

Length x width x height in inches / 231 = done

If you have a bigger tank with thick glass then make sure you subtract an inch or so, or be careful to measure inside dimensions.

You also measure for the top water level where it's at most of the time. Not the actual top of the tank.

Subtract 5-10% based on if you have a lot of substrate and LR.

Technically larger tanks, or long oneswill have a bit of bow in the middle increasing water volume, but it's not much. Does matter in the equation if you are SpaceX

 

[Bob Weigant]

I always knew my 180 didn't have a 180 gallons of water in it. Id have to estimate that it probably has 15 gallons less with all the rock. When I dose I try to keep that in mind