Volume or Illusion?

Well guess what, it works perfectly. I decided to use a 3 gallon top off for my experiment. I tested the salinity pre-topoff of my 85 gallon tank at 1.0225. You need to sort of extrapolate between the numbers on the hygrometer. I then made up 3 gallons of RO/DI water and just for kicks tested that at 1.000. I then topped of the tank, waited 2 hours to get a good mix and tested again, 1.0212. Now, subtract that from the 1.0225 and this took me a while to figure out but drop out the "1s" so you have .0225-.0212 = 0.0013. You then divide that by 0.0225 to get a percentage change, .0013/.0225=0.05777. Then divide that number into your the 3 gallons, 3/.05777=51.9 gallons. So my 85 gallon tank with about 150 lb LR, 2" of sand has 52 gallons of water. So if I need to treat or do something I now have an accurate number to work with.

I think if you have an accurate enough hygrometer you could do this with only 1 gallon and get a close number to how much water you really have, no guessing.

Thanks ReefSparky for getting the mental juices running.

 

LOL.

You got my juices running too. I decided to write a short article, a "how to" on this topic.

Read this.

enjoy.

 

I misspelled Hydrometer in my posts - sorry.

Good article but I think you may be doing more than necessary. Lets say I have a tank of unkown water volume and I do not care about what size it is. All I need to do is mearsure the salinity, add a known amount of pure water, measure the salinity again and use that percentage change with my known amount of added water and that is your volume of tank water. Or am I missing something?

 

Nope. You're not missing anything. I am! LOL.

 

In case of an over populated tank where you have to add a, or particular elements you can use this link below to figure out the amount of water in your tank, additives and more, it is a very handy tool, in case you didn't know where to find it.
3reef.com - Forums for coral reef aquariums, salt water fish, corals, inverts, protein skimmers, aquarium lighting and more! - Calculators

 

You will learn quickly that dosing will get you in trouble. As mentioned before, weekly water changes should be enough for your tank to replace anything removed. A good quality salt like coralife salt, has everything you need for a moderatly stocked tank.

 

Actually, those do not tell you how much volume to subtract for sand, rock etc, only the volume of an empty tank. There needs to be a simple way to find out how much actual liquid is in the tank and I think this thread between ReefSparky and I came to a fairly simple method.

I am not planning on adding any additives but was interested in how you would learn the real liquid volume of a tank and at least for a salt water tank we have it now. A fresh water tank needs a different method.

 

sorry about that sent you the wrong link...lol
here it is.....Aquarium System Volume Calculator

 

That is an interesting calculator but gave me a totally different number, 77 gallons vs 52 that comes out of the dilution method. I think the presumption in the calculator of volume of LR by weight is off. I know my 150 lb of LR required two 32 gallon cans to cure so only subtracting about 8 gallons for LR in the calculator does not seem correct. It also assumes your tank size, in my case 85 gallons is filled to the top which they usually are not.

Using the dillution method the weight and volume of sand, LR, fish or anything else does not matter, you are only working with the water volume in your entire system.

You might want to try it both ways and then use a gut feel on which way might be more accurate.

Fun stuff anyway.