How much of the water is needed for water change?

[homersimpsonlikesfish]

How much water do you need to remove from a FOWLR tank? Is it 10% or 20% each week? And why do you have to make a larger water change for goldfish tanks than saltwater tanks?

 

[PotatoPig]

For FOWLR the demands can be pretty low, especially if you have very low PAR on the tank.

Tropical Marine vs Freshwater Goldfish:

Reef /Tropical Marine tanks are set up with a large capacity to process ammonia, so the ammonia should be very quickly removed from the system. The nitrites and nitrates are also much less toxic in a marine environment than in freshwater so won’t harm the fish at any concentrations you’ll realistically achieve.

Tropical Marine tanks also tend to have a much lower fish biomass for their size than many freshwater tanks, as the fish typically need more space to swim, more territory, more hiding places and there are often limits on how many fish of any type you can include due to aggression. So these tanks are often churning out less waste than a freshwater tank of the same size.

I also understand goldfish put out a particularly large waste quantity even among freshwater fish, so need additional filtration/maintenance to accommodate that.

 

[AydenLincoln]

It’s going to depend on tank size! 5 gallons in a 20 gallon tank would be 20% or one bucket now in a 180 gallon tank or another massive tank 5 gallons is nothing and has very little effect. The larger the volume the bigger the water change a small water change in a big tank will be nothing compared to if it’s a nano.

 

[Gumbies R Us]

It’s going to depend on tank size! 5 gallons in a 20 gallon tank would be 20% or one bucket now in a 180 gallon tank or another massive tank 5 gallons is nothing and has very little effect. The larger the volume the bigger the water change a small water change in a big tank will be nothing compared to if it’s a nano.

I do 5 gallons for my 20 gallon tank!

 

[AydenLincoln]

I do 5 gallons for my 20 gallon tank!

Me too!

 

[RandyL]

I tend to favor smaller, more frequent water changes, so I’d favor the 10% on a weekly basis. Testing the big 3 (ammonia, nitrites, nitrates) plus others like hardness (dKH) and calcium will also help you find out what works for your tank.

 

[EeyoreIsMySpiritAnimal]

I tend to favor smaller, more frequent water changes, so I’d favor the 10% on a weekly basis. Testing the big 3 (ammonia, nitrites, nitrates) plus others like hardness (dKH) and calcium will also help you find out what works for your tank.

Why would you ever test for nitrites, and why test for ammonia once the tank is cycled??

 

[Miami Reef]

How much water do you need to remove from a FOWLR tank? Is it 10% or 20% each week? And why do you have to make a larger water change for goldfish tanks than saltwater tanks?

If it’s a FOWLR, I probably wouldn’t do any water changes.

If I had a nice FOWLR (show quality), I would invest in an ozone generator and activated carbon. The water would look much cleaner than even over 50% weekly water changes. Nothing can beat the clarity of ozone.

If nutrients are what you’re trying to lower, then there are much more effective, easier, and cheaper ways to lower them than changing water.

 

[homersimpsonlikesfish]

If it’s a FOWLR, I probably wouldn’t do any water changes.

If I had a nice FOWLR (show quality), I would invest in an ozone generator and activated carbon. The water would look much cleaner than even over 50% weekly water changes. Nothing can beat the clarity of ozone.

If nutrients are what you’re trying to lower, then there are much more effective, easier, and cheaper ways to lower them than changing water.

So basically, if my 20 gallon tank is only a FOWLR aquarium, it will clean itself? I plan to only have shrimp, hermit crabs, and 2 fishes. The live rock will clean everything?

 

[Idech]

How much water do you need to remove from a FOWLR tank? Is it 10% or 20% each week? And why do you have to make a larger water change for goldfish tanks than saltwater tanks?

Goldfish are the dirtiest fish in freshwater so that’s an extreme example. But in freshwater, you don’t have any tools to remove detritus from the water. In saltwater we have skimmers.

You also do WC in freshwater to remove nitrates, which will keep getting higher if you don’t, and harm fish.

In saltwater, nitrates tend to be low, even very low, almost inexistent. Especially in reef tanks.

 

[homersimpsonlikesfish]

Goldfish are the dirtiest fish in freshwater so that’s an extreme example. But in freshwater, you don’t have any tools to remove detritus from the water. In saltwater we have skimmers.

You also do WC in freshwater to remove nitrates, which will keep getting higher if you don’t, and harm fish.

In saltwater, nitrates tend to be low, even very low, almost inexistent. Especially in reef tanks.

So as long as I keep the number of fishes to a bare minimum level, I can get away with weekly 20% water changes and just do that once a month?

 

[littlefoxx]

Why would you ever test for nitrites, and why test for ammonia once the tank is cycled??

Well if you have fish that produce more waste like the predators I have in mine I like to know what the ammonia level is to keep it at zero for them and the other fish in the tank!

 

[homersimpsonlikesfish]

Well if you have fish that produce more waste like the predators I have in mine I like to know what the ammonia level is to keep it at zero for them and the other fish in the tank!

The only fish I plan to keep are at the most are just 2 chromis or 2 damselfish.

 

[EeyoreIsMySpiritAnimal]

Well if you have fish that produce more waste like the predators I have in mine I like to know what the ammonia level is to keep it at zero for them and the other fish in the tank!

So you're saying the tank's not cycled. Neat.

 

[littlefoxx]

So you're saying the tank's not cycled. Neat.

Nope it is, been running at the first guy’s house 4 years. I used almost all his water. Had it up in my house almost a year. You can have ammonia in cycled tanks, multiple threads on here with that happening. I dont have ammonia as I prefer to know what my levels are at all times by testing the water. Not testing for stuff would mean not knowing what the levels are. Not everyone does test which you clearly dont but some of us want to be proactive in water changes and know what our parameters are! Not a bad thing at all

 

[EeyoreIsMySpiritAnimal]

Nope it is, been running at the first guy’s house 4 years. I used almost all his water. Had it up in my house almost a year. You can have ammonia in cycled tanks, multiple threads on here with that happening. I dont have ammonia as I prefer to know what my levels are at all times by testing the water. Not testing for stuff would mean not knowing what the levels are. Not everyone does test which you clearly dont but some of us want to be proactive in water changes and know what our parameters are! Not a bad thing at all

Not a bad thing, just a waste of time and money, and bad advice for new reefers.
But you do you.

 

[littlefoxx]

The only fish I plan to keep are at the most are just 2 chromis or 2 damselfish.

I change my water if I read or detect any ammonia. Ive got a 70 and a 125 gallon tank. 70 I do smaller water changes on, the 125 I do a little bigger (15 gallons) a month typically since its cycled and I want to make sure my fish have fresh salt water too!

 

[homersimpsonlikesfish]

Not a bad thing, just a waste of time and money, and bad advice for new reefers.
But you do you.

Wait. I thought the live rock and live sand will eat the ammonia?

 

[littlefoxx]

Not a bad thing, just a waste of time and money, and bad advice for new reefers.
But you do you.

Its not bad advice, its just advice. Beautiful thing about the hobby is people do things differently and new reefers can take what they want from others experience to meld their own style. not trying to argue at all by the way just sharing my experience.

 

[EeyoreIsMySpiritAnimal]

Wait. I thought the live rock and live sand will eat the ammonia?

Correct. Once a tank is cycled (aka has enough nitrifying bacteria to handle the current bioload), unless there's a large addition of fish or a large amount of dead critters, the bacteria will keep up with the amount of ammonia produced by fish waste and uneaten food. No need to test ammonia if there's not an unexpected ammonia source.

And if you have coral, there's even less of a need since coral consumes ammonia and will further eliminate whatever is produced by waste, etc.