FOWLR Tank

[FlameangelLover]

Thinking of doing a Fowler tank. How often do FOWLR tanks need water changes? I do weekly on my mixed reef but how often does fowlr need it?

 

[Subsea]

Depends on bioload & nutrient management.

I have reef tanks that I don’t change water but once a year.

 

[fish_collector]

There are too many variables to offer a one size fits all answer.
What size tank?
Skimmer?
Filter sock?
Sand?
Rocks? Dry or live?
How many fish? What species?
How often does the sand need to be vacuumed?
Is there nuisance algae present?
What's your tolerance for where nitrate and phosphate should elevate to? (You may have a hard time finding conclusive data on this)

Fwiw, my 100g fowlr has nitrates and phosphates that are beyond what a Hanna tester will measure, yet my fish are healthy. I still change 15 or 20 gallons of water every 5 or 6 weeks though, not to dilute the nutrient levels but rather to discard the muddy water after I vacuum the sand.

 

[FlameangelLover]

There are too many variables to offer a one size fits all answer.
What size tank?
Skimmer?
Filter sock?
Sand?
Rocks? Dry or live?
How many fish? What species?
How often does the sand need to be vacuumed?
Is there nuisance algae present?
What's your tolerance for where nitrate and phosphate should elevate to? (You may have a hard time finding conclusive data on this)

Fwiw, my 100g fowlr has nitrates and phosphates that are beyond what a Hanna tester will measure, yet my fish are healthy. I still change 15 or 20 gallons of water every 5 or 6 weeks though, not to dilute the nutrient levels but rather to discard the muddy water after I vacuum the sand.

lol i definitely asked a question that is extremely nuisanced. I think a better question is . Because there is no corals what is the purpose of the water change? Is it purely for nutrient export? And how much nutrients is to much?

 

[fish_collector]

lol i definitely asked a question that is extremely nuisanced. I think a better question is . Because there is no corals what is the purpose of the water change? Is it purely for nutrient export? And how much nutrients is to much?

Understood.
I change water in my fowlr not to help with nutrients but rather to be able to siphon the sand and discard what ends up in the bucket, I guess you could call that nutrient export. There is a lot of brown stuff that gets siphoned out that I'd rather not leave in the sand, it's what I do and have had success with but not what others may do or recommend. I can say that it keeps the sand nice and white.

How much nutrients is too much for a fowlr? Let me know if you find the answer to that! Some say nitrate at 100 is the limit while I've read on this forum that 1000 won't hurt. I'm very in tune with my fish, I like and watch them much more than the corals in my sps tank, and I can say without a doubt that nutrients beyond what a Hanna will measure don't harm them at all. If I had to find an answer to this question I'd reach out to Jay Hemdal on this forum, he would have more knowledge on the subject than anyone else.

 

[FlameangelLover]

lol i definitely asked a question that is extremely nuisanced. I think a better question is . Because there is no corals what is the purpose of the water change? Is it purely for nutrient export? And how much nutrients is to much?

Understood.
I change water in my fowlr not to help with nutrients but rather to be able to siphon the sand and discard what ends up in the bucket, I guess you could call that nutrient export. There is a lot of brown stuff that gets siphoned out that I'd rather not leave in the sand, it's what I do and have had success with but not what others may do or recommend. I can say that it keeps the sand nice and white.

How much nutrients is too much for a fowlr? Let me know if you find the answer to that! Some say nitrate at 100 is the limit while I've read on this forum that 1000 won't hurt. I'm very in tune with my fish, I like and watch them much more than the corals in my sps tank, and I can say without a doubt that nutrients beyond what a Hanna will measure don't harm them at all. If I had to find an answer to this question I'd reach out to Jay Hemdal on this forum, he would have more knowledge on the subject than anyone else.

Thank you! I’m a big guy on “systems” because the tank will be so big I would love to do month 10-15% water changes but I don’t know if that is to little. And I don’t know what are signs to show it’s to little lol . You think this could work?

 

[fish_collector]

For a FOWLR, sure.

 

[Subsea]

Thank you! I’m a big guy on “systems” because the tank will be so big I would love to do month 10-15% water changes but I don’t know if that is to little. And I don’t know what are signs to show it’s to little lol . You think this could work?

“I would love to do month 10-15% water changes but I don’t know if that is to little. And I don’t know what are signs to show it’s to little lol .“

If your white substrate turns brown, it’s too little.

 

[JumboShrimp]

I rarely do a water change on my 150-gallon FOWLRs. When I had a large messy-eating predators, Nitrates would run 160+ ppm, Phosphates 10 ppm. Now that I have filled the tanks with Butterfly fish, I might change some water quarterly (as they are likely more sensitive fish), but I tested Phosphates yesterday for the first time in a long time, and even with pretty much zero water changes the reading was only 1 ppm. And I feed the Butterflies 4-6 times a day. (Again, no more messy-eaters like Clown Triggers, Lunare Wrasses, Emperor Angels, etc., so that's probably a big factor. ) As someone mentioned, using a large siphon regularly to clean the sand could be a good back-door way of replacing water. Just throwing out some ideas for you. You will love running a FOWLR though-- no doubt about it!

 

[fish_collector]

I rarely do a water change on my 150-gallon FOWLRs. When I had a large messy-eating predators, Nitrates would run 160+ ppm, Phosphates 10 ppm. Now that I have filled the tanks with Butterfly fish, I might change some water quarterly (as they are likely more sensitive fish), but I tested Phosphates yesterday for the first time in a long time, and even with pretty much zero water changes the reading was only 1 ppm Nitrates. And I feed the Butterflies 4-6 times a day. (Again, no more messy-eaters like Clown Triggers, Lunare Wrasses, Emperor Angels, etc., so that's probably a big factor. ) As someone mentioned, using a large siphon regularly to clean the sand could be a good back-door way of replacing water. Just throwing out some ideas for you. You will love running a FOWLR though-- no doubt about it!

The nitrate on your FOWLR is 1?

 

[JumboShrimp]

Ooops. My bad. Let me go edit that. "Phosphates" currently 1 ppm. Thanks. (Last time I check Nitrates a couple of months ago they were 66.1 via a Hanna checker.)

 

[FlameangelLover]

Ooops. My bad. Let me go edit that. "Phosphates" currently 1 ppm. Thanks. (Last time I check Nitrates a couple of months ago they were 66.1 via a Hanna checker.)

So what’s a sign to show me I need a water change or is 10% monthly fine and don’t worry about it lol

 

[JumboShrimp]

I can't really keep snails (because my Butterflies would eat them like mini- clams) still I have virtually no algae on my rocks and no funky-looking sand, and have to only do minimal front glass cleaning-- but if those things changed that would be a 'sign' to do more water changes. Also you need to know the appearance of your fish; sluggish fish or fish losing color would probably be signs that your water has gone without a change too long. I do run a skimmer in the sump with the return lines from the pump pointed at the tank's surface, plus a dedicated gyre pointed at the surface. I like to keep the water ultra-oxygenated, since I'm not doing the frequent water changes.

What kind of fish do you have in mi d for your FOWLR? (It feels as if I've had most of them, at one time or another. Lol!)

 

[fish_collector]

So what’s a sign to show me I need a water change or is 10% monthly fine and don’t worry about it lol

In a FOWLR there’s not much to worry about. Maintain salinity at 1.021 without giant swings and keep the temp between 76-81. There really isn’t a reason to change water, other than producing dirty water during maintenance that you’ll discard and replace with fresh saltwater.

Sounds too simple doesn’t it? Well it IS that simple. Everyone has the notion that strict water parameters be maintained with dosing and trace element additions and other completely unnecessary things, but in reality none of that matters for fish, they just don’t care about any of that. I wouldn’t lead you down a path if I thought it would harm your fish.

My imperator and rock beauty angels, chocolate and hippo tangs, foxface etc could care less what the salinity, nitrate and phosphate levels are, they just want to know when feeding time is again

 

[Fish Fan]

I agree with the replies above. I remember when keeping corals was very difficult, and many had just fish tanks with crushed coral substrate and dead, bleached coral for decorations. In these tanks, the fish didn't care how high your nitrate got, it would likely be the high hundreds to thousands of ppm before fish would care. I don't believe that phosphate at any level would be toxic to fish.

That said, N&P relate to algae growth. Back in the day it was common to have two sets of dead, bleached coral decorations so that you could re-bleach one set while having the other in your display. The algae was that bad.

Fish also don't use or care about micro nutrients (trace elements) in the water.

So to answer your question, I think it's possible to run a FOWLR without doing "typical" regular, partial water changes in an effort to control N&P or trace elements. I think it might be beneficial to change out water as part of your maintenance, like others have said, such as when cleaning the sand bed.

Given that this would be a fish only tank, you could completely remove the phosphate using something like GFO or Lanthanum Chloride (LC). This would eliminate ugly algae, but also eliminate desirable macro algae and coralline. In the way back, this was a way to keep a FOWLR.

I don't ever ask anyone to take my word for things like this, and I searched and I was able to find at least one post from Randy Homes-Farley where he comments on the toxicity of nitrate (he has a whole article on why nitrite is not toxic):

https://www.reef2reef.com/threads/no2-no3-toxicity.992846/post-12217079

I hope this helps and good luck!

 

[jonnywink]

So what’s a sign to show me I need a water change or is 10% monthly fine and don’t worry about it lol

I have a 55 gal. FOWLR and do a 15% about every 3 weeks. I also have a protein skimmer running all the time.

 

[fish_collector]

Keeping a marine fish tank is a balancing act between having enough white light to illuminate the fish and bring out their colors while keeping algae in check. I'm not sure that the amount of available nutrients correlates directly with the speed at which algae grows. I think it's more complicated than that down on a microbial level but that's out of my realm of knowledge so I'll leave it at that.

I'm not an ichthyologist so I don't know for sure but there may be some trace elements, if present in the right concentration, that would benefit fish, perhaps even be necessary for life processes but that's just speculation. Certainly doing small regular water changes during maintenance would replenish them. 40 years ago when I started keeping marine fish only tanks (couldn't call them a fowlr yet because we used dead bleached coral) I would add Tropic Marin trace elements on a regular basis. It probably didn't accomplish anything but it made me feel good that I added it anyways.

Back then I had a Truvu 240 with undergravel filter plates and about 3" of medium grade crushed coral substrate, it wasn't called aragonite yet. The undergravel plates were made of eggcrate with a 2" border melted on to raise it up off of the tank bottom, and then it was covered with nylon window screen, using a soldering iron to melt it to the eggcrate around the edges. There were 4 plates to cover the entire tank bottom, and 4 bulkheads installed, one under each plate. These went to the return pumps underneath and back to the tank. Because all of the water flow went through the sand bed, it was imperative that it be vacuumed on a regular basis. There was no filter socks or fleece rollers back then, the sand bed was everything but I can say that it worked quite well, so much so that I've thought about using that method again. Some hobbyists used a reverse flow undergravel filter but I never went down that avenue. Back then getting information about trends wasn't easy, it was either something a LFS told you about or from the few magazines that were available, and that's it.

One day I read about how to drill the tank at the water level for a drain down to a sump, so then a protein skimmer could be used. I bought all of the hardware and a 20g acrylic tank and went to town, and in an afternoon I had a functioning sump! I saved up some more money and bought a Sander external skimmer that ran off of wooden airstones, no venturis or needle wheels yet this was 1989. Soon after that I added an ozone generator and in a few days I had water so stinking clear it was amazing!

I've got probably only a few photos of my old 240, remember this was well before cell phone cameras. If you wanted to take a picture, you had to use a film camera and have it developed which took 4-5 days. I'll see if I can dig one of them up and I'll post it here.

Anyways just going down memory lane, I really wish I had kept some of my original equipment like my Sander protein skimmer, it was a neat piece. I'm sure Fish Fan can tell some similar stories from way back when

 

[FlameangelLover]

I can't really keep snails (because my Butterflies would eat them like mini- clams) still I have virtually no algae on my rocks and no funky-looking sand, and have to only do minimal front glass cleaning-- but if those things changed that would be a 'sign' to do more water changes. Also you need to know the appearance of your fish; sluggish fish or fish losing color would probably be signs that your water has gone without a change too long. I do run a skimmer in the sump with the return lines from the pump pointed at the tank's surface, plus a dedicated gyre pointed at the surface. I like to keep the water ultra-oxygenated, since I'm not doing the frequent water changes.

What kind of fish do you have in mi d for your FOWLR? (It feels as if I've had most of them, at one time or another. Lol!)

So I really am only going fowlr until December then adding my corals. Once December hits I will do a 100% water change and add in all corals . But while it’s fowlr there will be a lot of small fish seeing that I don’t really like big fish. So a bunch of goby’s and small wrasse and my favorite fish ever. FLAME ANGEL

 

[FlameangelLover]

So what’s a sign to show me I need a water change or is 10% monthly fine and don’t worry about it lol

In a FOWLR there’s not much to worry about. Maintain salinity at 1.021 without giant swings and keep the temp between 76-81. There really isn’t a reason to change water, other than producing dirty water during maintenance that you’ll discard and replace with fresh saltwater.

Sounds too simple doesn’t it? Well it IS that simple. Everyone has the notion that strict water parameters be maintained with dosing and trace element additions and other completely unnecessary things, but in reality none of that matters for fish, they just don’t care about any of that. I wouldn’t lead you down a path if I thought it would harm your fish.

My imperator and rock beauty angels, chocolate and hippo tangs, foxface etc could care less what the salinity, nitrate and phosphate levels are, they just want to know when feeding time is again

Thank you for this bro you just gave me the confidence to just do it lol. I’ll do monthly water changes just for good measure and then just let it vibe. I’ll monitor fish closely was well

 

[FlameangelLover]

Keeping a marine fish tank is a balancing act between having enough white light to illuminate the fish and bring out their colors while keeping algae in check. I'm not sure that the amount of available nutrients correlates directly with the speed at which algae grows. I think it's more complicated than that down on a microbial level but that's out of my realm of knowledge so I'll leave it at that.

I'm not an ichthyologist so I don't know for sure but there may be some trace elements, if present in the right concentration, that would benefit fish, perhaps even be necessary for life processes but that's just speculation. Certainly doing small regular water changes during maintenance would replenish them. 40 years ago when I started keeping marine fish only tanks (couldn't call them a fowlr yet because we used dead bleached coral) I would add Tropic Marin trace elements on a regular basis. It probably didn't accomplish anything but it made me feel good that I added it anyways.

Back then I had a Truvu 240 with undergravel filter plates and about 3" of medium grade crushed coral substrate, it wasn't called aragonite yet. The undergravel plates were made of eggcrate with a 2" border melted on to raise it up off of the tank bottom, and then it was covered with nylon window screen, using a soldering iron to melt it to the eggcrate around the edges. There were 4 plates to cover the entire tank bottom, and 4 bulkheads installed, one under each plate. These went to the return pumps underneath and back to the tank. Because all of the water flow went through the sand bed, it was imperative that it be vacuumed on a regular basis. There was no filter socks or fleece rollers back then, the sand bed was everything but I can say that it worked quite well, so much so that I've thought about using that method again. Some hobbyists used a reverse flow undergravel filter but I never went down that avenue. Back then getting information about trends wasn't easy, it was either something a LFS told you about or from the few magazines that were available, and that's it.

One day I read about how to drill the tank at the water level for a drain down to a sump, so then a protein skimmer could be used. I bought all of the hardware and a 20g acrylic tank and went to town, and in an afternoon I had a functioning sump! I saved up some more money and bought a Sander external skimmer that ran off of wooden airstones, no venturis or needle wheels yet this was 1989. Soon after that I added an ozone generator and in a few days I had water so stinking clear it was amazing!

I've got probably only a few photos of my old 240, remember this was well before cell phone cameras. If you wanted to take a picture, you had to use a film camera and have it developed which took 4-5 days. I'll see if I can dig one of them up and I'll post it here.

Anyways just going down memory lane, I really wish I had kept some of my original equipment like my Sander protein skimmer, it was a neat piece. I'm sure Fish Fan can tell some similar stories from way back when

This is so good man I love hearing peoples stories in this hobby. I’m 27 and I think I’ll always have a saltwater tank for the rest of my life. My current favorite fish are Flame angel and copper banded so that’s who will rule my tank