Water Chemistry Question

[Bmitchell486 554]

I have a water chemistry question about Nitrates.

History:
My 72 has been set up for almost 7 years.  I've got 6 goldfish in there, overstocked.  I've got 3 ryukins that are almost 7 years old, and are 6 inches (including their long tails).  The other 3 are ranchu -- one is 4.5 inches, one is 3 inches, and one is 2.5 inches (including tails).

My maintenance routine:
I change ~80% of water once a week.  I service the filter (rinse out all media in a bucket of tank water) every 6-10 weeks.  I regularly test my water (API Master Kit), typically once a week right before I do my water change.  Occasionally I spot check my pH bc I'm curious to see how it fluctuates throughout the day.  

Food:
They get repashy gel food 1-2X a day.  They get bloodworms 4-5 times a week.  They can't have any pellets anymore because it makes one of my old fish float, and it makes another one of my old fish bottom sit.

My question:
Why, in the ~3 years since I've regularly tested my water, have I never seen a reading of Nitrates?  About 6 months ago, I let my tank go for 2 whole weeks without a water change, continued feeding regularly, and my nitrates read 0.  I decided to do this experiment again -- I just went 3 weeks without a water change, tested my water this morning and nitrates are zero.  I following the testing instructions exactly, and the kit is newer.  Keep in mind, I fully understand that there is plenty of organic waste that builds up and that Nitrate is just one type.  Any waste build up is bad, not just Nitrate.  I kept a close eye on my fish the whole time, they remained active, no bottom sitting or pouting.  Their behavior has remained perfectly normal.  I am sure there is organic waste built up after 3 weeks of no water changes, but why are my Nitrates still 0?!?!

I've read conversations online where someone says "My goldfish is sick, my tank in cycled, my ammonia/nitrite/nitrate is 0, what's wrong?" And the response I typically see from at least 1 responder is "A cycled tank never has a nitrate reading of 0.  Zero nitrates means your tank is not cycled.  You should always see a nitrate reading." 

So am I missing something? Thanks in advance for reading!  Just looking to learn.

 

[Bmitchell486 554]

Sidenote - I've seen ~5 PPM Nitrate reading a few times in my pond since it was set up last spring.  I'm just talking about my 72 in this thread.

[shakaho 6,312]

Well, if you saw someone on here say that a cycled tank never has 0 nitrates, you should have also seen my vigorous objection.  You have zero nitrates in your tank because you have denitrifying bacteria in your system.  Denitrifying bacteria can be found  just below the surface of substrate, in sumps that have collected some muck in the bottom, and in filters -- particularly dirty filters.  Although microbiologists have just started realizing the diversity of denitrifying bacteria, the ones most commonly found in fish tanks and small ponds thrive under anoxic (low oxygen) conditions, ideally close to nitrifiers that "feed" them nitrate and also lower the oxygen concentration to the levels they prefer -- just a little bit.

In substrate, the nitrifiers live in the surface area where they find a good oxygen supply and lots of ammonia from the fish.  The denitrifiers live just below them in an area of low oxygen and abundant nitrate which they convert to nitrogen-containing gases,  ideally to nitrogen gas.  In a filter, particularly one with a lot of debris caught, denitrifiers can live in anoxic pockets, surrounded by the biofilm that contains nitrifiers making nitrate for them.  The bigger the filter and the less often it gets clean, the more likely it will support a stable population of denitrifiers.

A well-established pond with a nice big biofilter usually has little to no nitrate.  This usually gets blamed on plants and algae using the nitrate, but you can find the same nitrate levels in some ponds with no plants and clear water.  Denitrifiers.  In contrast, look at a koi pond with state-of-the-art filtration.  Virtually every speck of debris gets removed from the water by the seive before it gets to the highly aerated moving bed biofilter.  Then it may go to a shower before it returns to the pond.  The water comes out clearer than tap water, but it accumulates nitrate just like an aquarium.  No denitrifiers in all that high-oxygen water.

This review article, while rather old, has a lot of good information on denitrification. 

 

 

[koko 14,335]

1 hour ago, shakaho said:

Well, if you saw someone on here say that a cycled tank never has 0 nitrates, you should have also seen my vigorous objection.  You have zero nitrates in your tank because you have denitrifying bacteria in your system.  Denitrifying bacteria can be found  just below the surface of substrate, in sumps that have collected some muck in the bottom, and in filters -- particularly dirty filters.  Although microbiologists have just started realizing the diversity of denitrifying bacteria, the ones most commonly found in fish tanks and small ponds thrive under anoxic (low oxygen) conditions, ideally close to nitrifiers that "feed" them nitrate and also lower the oxygen concentration to the levels they prefer -- just a little bit.

In substrate, the nitrifiers live in the surface area where they find a good oxygen supply and lots of ammonia from the fish.  The denitrifiers live just below them in an area of low oxygen and abundant nitrate which they convert to nitrogen-containing gases,  ideally to nitrogen gas.  In a filter, particularly one with a lot of debris caught, denitrifiers can live in anoxic pockets, surrounded by the biofilm that contains nitrifiers making nitrate for them.  The bigger the filter and the less often it gets clean, the more likely it will support a stable population of denitrifiers.

A well-established pond with a nice big biofilter usually has little to no nitrate.  This usually gets blamed on plants and algae using the nitrate, but you can find the same nitrate levels in some ponds with no plants and clear water.  Denitrifiers.  In contrast, look at a koi pond with state-of-the-art filtration.  Virtually every speck of debris gets removed from the water by the seive before it gets to the highly aerated moving bed biofilter.  Then it may go to a shower before it returns to the pond.  The water comes out clearer than tap water, but it accumulates nitrate just like an aquarium.  No denitrifiers in all that high-oxygen water.

This review article, while rather old, has a lot of good information on denitrification. 

 

 

Great post. Makes alot of since. I had a tank long ago that had 0 nitrates in it, it was a heavily planted tank. I always thought it was the plants. but this make more since to me

[Bmitchell486 554]

How interesting!  I can't wait to read that article later today.  I bet I have a combination of denitrifiers living in my filter and substrate (sand).  I only clean my filter every 6-10 weeks.  As much as I want to do it once a month... I seem to always let it go longer than that.  It's never caked with debris, but the sponges always rinse brown stuff out of them.

So Sharon, in light of what I read from above... What do you think is better? Cleaning the filter more consistently (say every 2 weeks) or doing it less often (say every 6 weeks) so the denitrifiers build up?

Also, about 10 minutes before each water change, I remove all ornaments from my tank and I rake my fingers through my sand, really churning it up.  I do this so no pockets of nasty build up.  But each time I do this, and I disturbing the nitrifiers and denitrifiers? Do they seem to recover pretty quickly after stirring up the substrate? What is more beneficial.... mixing up the sand, or leaving it alone to let the nitrifiers and denitrifiers do their job?

I apologize if the article answers these questions -- I'll be sure to read it later today.  Also, thank you Sharon for taking the time to give so much detail.  I am always striving to learn so I can provide the best system for my goldfish so that they are comfortable and healthy.

[shakaho 6,312]

If you have good water and healthy fish, you have no reason to change your filter-cleaning schedule.  Since you have no nitrate, you already have as many denitrifiers as your tank can maintain, just as no ammonia and no nitrite means you have as many nitrifiers as your system can maintain.  

How deep is your sand?  Does it have plants?  Stirring stand has always seemed pretty useless to me unless one wants to produce cloudy water.  The fish thoroughly enjoy doing that for you.  And what is a "pocket of nasty" anyway?   

[Bmitchell486 554]

Awesome.  I won't mess with what I'm doing, since everyone seems to be happy.  My older fish are lazier than they used to be, but still seem healthy to me.

My sand is ~1 inch thick.  I've been considering removing some so that it's 1/2 inch.  I have some java fern in there, but it's not really enough to provide a whole lot of benefit.  I just have it in there for aesthetic reasons

A while ago I saw a post and subsequent comments on FB about sand.  People recommended stirring the sand up before water changes.  They said pockets of harmful gas or bacteria could grow in warm water if left untouched.... so that's why I do it.  I rinsed the HECK out of my sand to rid it of dust before putting it in my aquarium so it doesn't make the water cloudy at all when I stir it.  But you're right, the goldfish sift through it on their own anyways.  They don't get to the bottom though, which is why I was considering removing some.  I've also been wanting to add some snails that dig into the sand (like I had in my saltwater tanks) but all I've found are the assassin snails.  I read that they actually do kill other snails, and I'd feel bad if my nerites were killed so I haven't added any of the assassin snails.  

[shakaho 6,312]

This is one of the many aquatic legends that get passed around the internet.  Everybody has read it many times, so it must be true,and so they repeat it.

How does one determine whether to believe it?  Just find the person who says, "I had an inch of sand in the bottom of my goldfish tank and didn't stir it up.  Then stuff rotted under neath the sand, toxic gasses bubbled up and my fish died!"  You won't find it because it didn't happen.  If anyone who warned against unstirred sand had a personal experience, they would report it.  ( And probably exaggerate it.)

What substrate do you find in natural ponds and lakes where goldfish live?  Sand.  Deep sand.  Goldfish feed at lake bottoms by taking a mouthful of sand and very skillfully spitting out the sand and swallowing the organic material.  They get little nutrition out of a mouthful, which explains why goldfish want to eat nonstop.  

I once had the clever idea of topping off the pots of water lilies with sand so debris wouldn't collect in the stones.  I put an inch or so in each pot.  It looked so nice and clean.  Within a week, the sand was gone from every pot.  It looked like someone had vacuumed the sand from the stones.   Some one had -- the goldfish.  

How could waste bury itself in the sand at the bottom of the tank?  Sand packs tight.  Debris lays on top of it.  Small debris can sink into aquarium gravel, and a layer of stones can hold a lot of rotting debris.

If your sand serves only to give your goldfish something to forage through (as opposed to anchoring plants), a quarter inch or so will do fine, so feel free to remove as much as you want to.

 

[Bmitchell486 554]

This is why I post here at Koko's  And Sharon, you know that I highly value the knowledge that you pass along.

I had the question in my mind as well about how logical that sand needs to be stirred up to release gasses/waste.  I spent a LOT of time swimming in a pond when I was a kid.  The water was brownish, and the bottom was really squishy, cool mud.  We usually chose to jump off the dock, verses wading in from the shore so that we didn't have to sink our feet into the mud.  My grandfather kept catfish and blue gill stocked at a density that required them to be fed by humans daily.  If he didn't feed, the fish population would reduce, and the fish in the pond were a food source for my grandfather (and us when we visited) so he wanted to keep their numbers up.  I suppose the build up of organic waste controlled the population from growing too large though.  Anyways, remembering swimming in that pond (haven't been swimming in there for probably 10 years!) always has me thinking about the natural state that pond fish live in verses the aquariums we keep them in.  Of course, I want to keep a higher density of fish per gallon in my aquarium than you would find in that pond, so I can't keep it all natural (and I haven't decided to try to get into aquaponics yet).  But the pond fish thrived in the brown water with a deep muddy bottom.  

Anyways, all that to say that I have seen many rumors passed along over and over online, many of which you have either validated or invalidated.  Thinking through my memories of swimming in a pond with healthy fish and a muddy bottom also validate that harmful gases and waste do not seem to build up under the surface of substrate.  I think my goldfish enjoy sifting through it.

And like I said, it is my aquarium with sand that has a 0 nitrate reading every week.  I've occasionally seen the 5ppm nitrate reading on my stocktank pond without a substrate.  It has me considering adding a little sand to the bottom of my little pond to give a home to some denitrifiers :-D

[Bmitchell486 554]

Also, I think you should consider adding a "myth-busters fact or fiction" section.  We can create a thread where people can post myth's that they've heard, or can post some outrageous advice that they've heard over and over that they're not sure about.  And then you and the other mods could tackle a few myths a month in their own dedicated thread.  You guys either validate as fact or invalidate as fiction, and keep the topics locked so that only the mods could provide proven information (people can still ask questions on the main thread).  That way, people like me could read through them.  And it would probably be my favorite section to go through, as you guys address new topics.

Not sure if you guys have time to do that (since I'm sure you're busy helping people in the D&D sections quite a bit) but it's just a thought. The information that you guys give out is tremendously helpful.

[Arctic Mama 3,625]

I have actually had substrate burp methane and carbon dioxide to the surface, for what it's worth.  But it was a dirt tank topped with sand and the clay/dirt substrate was very dense.  The decay was entirely predictable and stirring it would have just made a mess.  But I was aware of the dissolved gasses in the water and kept an eye on the behavior of the fish as the dirt tank aged.

Edited January 30, 2017 by Arctic Mama

[shakaho 6,312]

How did you identify the methane and carbon dioxide?

[shakaho 6,312]

17 hours ago, Bmitchell486 said:

Also, I think you should consider adding a "myth-busters fact or fiction" section.  We can create a thread where people can post myth's that they've heard, or can post some outrageous advice that they've heard over and over that they're not sure about.  And then you and the other mods could tackle a few myths a month in their own dedicated thread.  You guys either validate as fact or invalidate as fiction, and keep the topics locked so that only the mods could provide proven information (people can still ask questions on the main thread).  That way, people like me could read through them.  And it would probably be my favorite section to go through, as you guys address new topics.

Not sure if you guys have time to do that (since I'm sure you're busy helping people in the D&D sections quite a bit) but it's just a thought. The information that you guys give out is tremendously helpful.

We should "bust" some myths and ignore others, but we can't possibly take on many of them.   We put in several hours a day on sick fish.  

I searched for hours for an article for non-scientists on denitritification in aquariums with reasonable accuracy.  I couldn't find one.   The review article I linked you to will be heavy reading for most.  I could write an article on denitrification, but it would take days of full-time work since I simply can't make statements without a valid source.  

 

 

[Arctic Mama 3,625]

9 hours ago, shakaho said:

How did you identify the methane and carbon dioxide?

Just by process of elimination on what was making sulpherous smelling swamp gas bubble out of the substrate in pockets, so I could be off on the exact gasses - I wish I'd been able to actually test it but the smell was the only clue alongside fish behavior so decay was a factor. It also didn't happen for at least a year of the tank running with nothing disturbing the substrate but some roots.

Edited January 31, 2017 by Arctic Mama

[Bmitchell486 554]

On 1/31/2017 at 7:19 AM, shakaho said:

We should "bust" some myths and ignore others, but we can't possibly take on many of them.   We put in several hours a day on sick fish.  

I searched for hours for an article for non-scientists on denitritification in aquariums with reasonable accuracy.  I couldn't find one.   The review article I linked you to will be heavy reading for most.  I could write an article on denitrification, but it would take days of full-time work since I simply can't make statements without a valid source.  

 

 

Completely understand! It's amazing to me how you all make sure you're available at all times to help with emergencies and sick fish. You're dedicated, and I'm sure it takes more time than most of us realize.

 I read the original article you posted.  I did pretty well in biology/chemistry in high school/college so I was able to follow a lot of it.  

Thank you for searching fora non-scientist denitrification article! I am always eager to read what you write, but it sounds like it would be too much work for you to write an article.  My original question was answered and I'm good to go  I appreciate your dedication to only make statements from a valid source, and give advice only from your extensive experience.

[Butterfly 485]

So maybe I should stop cleaning my canisters so often... would make life easier.

I would be interested to know what your nitrates read a few days after you clean you canister (and how dirty it is when you clean it).


Sent from my iPhone using Tapatalk

[Bmitchell486 554]

On 2/4/2017 at 11:47 AM, Butterfly said:

So maybe I should stop cleaning my canisters so often... would make life easier.

I would be interested to know what your nitrates read a few days after you clean you canister (and how dirty it is when you clean it).


Sent from my iPhone using Tapatalk

The next time I clean out one of my canisters, I'll test a few days later and let you all know in this thread.

How often are you cleaning your filters now? 

I usually service mine every 6 weeks, but occasionally I go another week or two.  It's been a long time since I've gone 10 weeks.  Anyways, I rinse the sponges out in my tap.  They don't have visible debris on them, but the water rinses brown for about a minute before it rinses clear.  The majority of my filter is the ceramic beads, which I rinse in tank water.  Since the sponges catch all of the debris, they rinse pretty clean and the water is still pretty clear.  I have a fluval 406 running.

[FishTankEnthusiast 30]

This is a great thread! Very interesting so far and I can't wait to keep reading the discussion.

I will admit that I am naughty and I don't test my water very often. Only for fun, sometimes. I will have to start testing more often and see what I get, now that my tank is more established and heavily planted. 

The last time I tested was right before a water change, and I do 80-90% once a week. I remember my Nitrate being about 20ppm and I expected it to be higher, but I put it down to having plants in the tank. 

[shakaho 6,312]

A heavily planted tank will  often have no measurable nitrate, but not entirely because the plants use up the nitrate.  Aquatic plants use ammonia as their main nitrogen source, but will use nitrate if that's the only thing available.  The plants may use so much ammonia that the nitrifier population gets little, and thus produce little nitrate and the plants may use that up. 

You can't beat a live-fish-centered aquaponics system for water purification.  The terrestrial plants will use the nitrate, but they also use up a lot more, including organic chemicals, which can you can otherwise remove only by water changes (or well-maintained carbon if the organics come from the tap).   By live fish centered, I mean that one has water purification as the primary purpose of the aquaponics system.  That doesn't mean you won't get a lot of plants to feed you and the fish.  

A commercial aquaponics produces vegetables and fish with something less than 5% of the water needed for growing the plants and fish separately.

You can read more about aquaponics here and here.   

[Bmitchell486 554]

Update!

I decided for the last 2 months to clean out my canister filters every 4 weeks (just for funzies, not as a result of this thread).  I service my filter on the same day as water change day.  I tested nitrates each time 3 days after I cleaned the filters out -- Nitrates still 0.  Prior to each weekly water change, the Nitrates were also 0.  Common sense would tell me the denitrifiers are in my sand.

I also have not "stirred" the sand (raked my fingers through it) since I made the original post in January.  Everything looks/smells/tests the same.  I've got a 29 with sand (that one's at 1/2 in depth though).  I put the 29 on the same filter maintenance schedule, and also quit raking the sand.  This tank had nitrates showing up for the first 3-4 months I had it set up (been set up for 1/1/2 years now), so I didn't mention it in the original post.  But this tank also has had 0 nitrates when I test 3 days after the filter cleaning, and right before each weekly water change.