Is adding volume equal to water change?

[s7even]

I am cycling a new tank and decided not to fill it completely. It is an 88 gallon display tank with a 24 gallon sump. I filled the tank to about 60 gallons, so it covers all the rock.

I understand that I should do a large water change when the tank cycles. If I fill the tank and sump, will that count as a 52 gallon water change?

[Half Vaped]

When we perform a water change, we're essentially just diluting the accumulated NO3, PO4 and other junk in the water. So in a sense, yes, adding more clean water has the same effect.

How's your ammonia, nitrite and nitrate levels measuring up? If they're real high, it may help to take out some water anyways. Always better to set yourself up for the highest chance of success.

[s7even]

The tank is still in the begining of the cycle. It appears that the ammonia is dropping while the nitrites are up.

I used dry Pukani and am currently ghost feeding frozen mysis shrimp. I'm not all that confident cycling with no live rock.

I appreciate the response.

[whosurcaddie]

NO no no no, adding water does not remove nitrate and phosphate. They become more concentrated as your water evaporates, but they are never removed just by adding freshwater.

You need water changes and other forms of nutrient removal. A GFO reactor is a great addition to lower phosphate, but there are many methods to nutrient removal from algae scrubbers to carbon dosing. You have to find what works for you.

[whosurcaddie]

I would also look into getting an auto top off so you wont be filling your tank constantly. I have an AutoAuqua Smart ATO that I love, but there are cheaper versions out there as well.

This will keep your salinity stable and provide less swing in your parameters. Add to that not having to top the tank off every day. I wouldn't run a reef without one.

[Half Vaped]

I think the other dude is speculating that you had 88 gallons filled to the top and you let it evaporate down to 60 gallons. And that you were going to add freshwater to get the salinity back where it should. If that were that case, then no dilution is taking place.

How I understand your case, only 60 gallons were ever put in the tank in the first place and you now plan to add 52 gallons of saltwater. In this case, yes, dilution is absolutely taking place.

Let's say the displacement of your rock is 8 gallons (to make the math easy), so you have 52 gallons of saltwater in the tank. Adding an additional 52 gallons of saltwater will have the exact same effect as a 50% water change.

But he brings up a good point about the ATO. If you don't already have one, it should be one of your first purchases once you have the sump running.

And if you aren't already adding freshwater everyday, you need to look into that. Depending how well-covered the tank is, the water temp and the room's temp and humidity, you may be losing up to five gallons a day in a tank that size. But probably less.

Get a refractometer as well if you don't have that either.

[JZinCO]

NO no no no, adding water does not remove nitrate and phosphate. They become more concentrated as your water evaporates, but they are never removed just by adding freshwater.

You need water changes and other forms of nutrient removal. A GFO reactor is a great addition to lower phosphate, but there are many methods to nutrient removal from algae scrubbers to carbon dosing. You have to find what works for you.
Jumping on with what others said, see below

I'l simplify the numbers:

50gal with 1ppm NH3 yields 50gal with a concentration of 1ppm NH3.
50gal with 1ppm NH3 plus 50gal with 0 ppm NH3 yields 100gal with a concentration of 0.5ppm NH3

The latter is equivalent to starting with 100gal with a concentration of 1ppm NH3 and replacing 50% with water containing a concentration of 0ppm NH3.

So to the OP, yes.

[Geissijs]

to jump in here, it would be wise to remove some water when you add your final 52 gallons. the concentration of the ammonia will change to nitrite then to nitrate, hence the cycle. if you don't remove it early, while you've got the chance, you may set yourself up for a problem with nitrate battle down the road.

@JZinco, your math is correct, but the logic behind allowing the concentration to stay in the tank will only compound problems later. it will take time to get fish/corals into the tank, why wait until later to remove the excess, do it now while its small

[ericarenee]

what i do not get .. you have 88 gallon tank and 24 gallon sump.. How is the system running and cycling without the tank full of water.. The water would not reach the overflow that should be skimming the surface of the tank water..

the complete system needs to be up and running to cycle properly..NOT to mention adding that much (FRESH)Water in a tank this is not running as it would be setup might cause another cycle ..

i say
set the tank up and run it complete let it cycle and do water changes as you should..
if your trying to save money by cycling with a bit over half capacity of water your prob in the wrong hobby. Its expensive but cutting corners like this will only cost you more in the long run..

Good Luck

[JZinCO]

@JZinco, your math is correct, but the logic behind allowing the concentration to stay in the tank will only compound problems later. it will take time to get fish/corals into the tank, why wait until later to remove the excess, do it now while its small
I hear ya, and IMO, that goes into the personal preference category (water changes during cycling). And OP didn't post numbers so it's hard to tell what's going on with water quality.

[s7even]

what i do not get .. you have 88 gallon tank and 24 gallon sump.. How is the system running and cycling without the tank full of water.. The water would not reach the overflow that should be skimming the surface of the tank water..

the complete system needs to be up and running to cycle properly..NOT to mention adding that much (FRESH)Water in a tank this is not running as it would be setup might cause another cycle ..

i say
set the tank up and run it complete let it cycle and do water changes as you should..
if your trying to save money by cycling with a bit over half capacity of water your prob in the wrong hobby. Its expensive but cutting corners like this will only cost you more in the long run..

Good Luck

I am cycling the tank as if it were a 60 gallon tank with no overflow. I have powerheads, heater, sand, dry pukani rock. This feels no different than my first tank, which was a basic 55 gallon with no overflow.

I figured that I did not need to use the whole system while cycling since the biological filtration was the sand and rock. Since there aren't any fish or coral in the tank, I did not feel like the extra water volume would help. If I am wrong, Please advise.

When the tank is cycled, I was going to add the rest of the fresh saltwater to the system, so that the sump, Ato, skimmer, carbon reactor, and gfo reactor are in use. Do I need those running while I am cycling?

Thanks for the assistance. It sounds like I will do a water change and add the extra saltwater when the tank is cycled.

[anthonys51]

to be honest no you dont need to run those during cycle, but they also cant hurt either and the only thing you gained was saving 20-30 gallons of saltwater. imo i would of set up the tank normal and then did a water change, but yes you can also do it your way.

the only did like the one person said watch your salinity because of evaporation, you be surprised how much can come out in 4-8 weeks.

but having 90 and taking out 20 or starting with 70 and adding 20 is the same thing.

a water change is 2 separate actions
first taking out 20 gallons
2nd adding 20 gallons

you dont have to do the first to do the 2nd. well most of us do because our tank would overflow but you dont