Controlling Nitrates in Unplanted Tank

[Taurus]

My goal is to keep nitrates under 20 ppm with only a weekly 50% water change in my 20g long tank. Currently it's taking two 50% water changes per week.

Here what I've done so far.

1. Reduced gravel bed from 2" to 1". I was unable to thoroughly vaccum through the 2" bed so over time uneaten food and debris was accumulating in the 2" bed. I removed 1" of gravel and stirred up the remaining leaving a 1" bed that I can thoroughly vaccum. That means less gravel for beneficial bacteria, but should produce fewer nitrates?? Nitrates are currently testing at around 5 ppm after lowering gravel bed.

2. I'm running both AC filters with one sponge in the bottom, 1" layer of filter floss, an the solid biomax cylinders that come with the AC filters up to the spillway on the filter outlets.

Again, no plants in the tank.

Should I consider eventual replacement of biomax in the filter with the Eheim Pro Substrate?

Comments\replies are appreciated.

Thanks

[mduros]

It's your bio-load my friend...  You're not going to be able to keep those nitrates down without plants with that number of fish.  It's just not going to happen.  And plants wouldn't help too much either.  Either rehome some of your fish to ease your burden and theirs, or keep up those two water changes a week.  Sorry to be the barer of bad news.

Oh, one other thing I just thought of.  What is your feeding schedule like?  They will do perfectly fine with skipping a couple of feedings a week and that will also relieve the nitrates.
Take care,
Mary.

[Taurus]

Ah, I should have a third action item.

3. Feeding corys ever other day with Hikari Sinking Wafer. I bought a resin reptile feeding dish an placed it on top of the gravel. The sinking wafers go into that dish (about 1/2" sides) and the cory find them there. Hopefully less wafer goes into the gravel. I feed the Harlequins and Pristellas Hikari Micro Pellets (flloating) and they are devoured within a minute. Both Harlequins and Pristellas tend to swoop in for a bite or two of the sinking wafers. LOL..it's fun to watch the competition over the sinking wafers.

And yes, I've read that adding plants wouldn't be of that much help because in lowering nitrates. I'll be testing daily for nitrates for the next week to see if the level approaches 20 ppm or higher.

[Taurus]

Either rehome some of your fish to ease your burden and theirs, or keep up those two water changes a week.  Sorry to be the barer of bad news.

Mary.

Mary,
  That's not bad news..if it takes two water changes then so be it. And I've read that both Eheim Pro substrate and Seachem Matrix may help to lower nitrates because of internal pore anaerobic area where nitrates are turned into nitrogen gas and off gased by water surface movement. I don't know whether it's true or just a new marketing spin.

Taurus

[Taurus]

Description of Seachem's Matrix biomedia.

http://www.bigalsonline.com/BigAlsUS/ctl3684/cp18401/si3637830/cl0/seachemmatrixbiomedia500ml

[RTR...Grumpy Ole Fogie]

Clarifications:

1. You want nitrate.  If nitrate production stops or slows or is reduced, you will have either nitrite, or ammonia, both toxic to fish.  Live oxygen-breathing critters generate nitrogen-containing waste.  The whole point of bofiltration is to detoxify the forms of waste which are diluted out of toxic range in the wild else the environment would not support the fish.   If you want lower nitrate production, reduce the bioload and be very sure that you do not over-feed (most hobbyists over-feed or inappropriately feed massively).  Most fish have no shut-off feedback mechanism when they are full, they just keep eating even though undigested or partially digested food is being excreted.   That is no more healthy for the fish (or the tank) as it is for humans with similar practices.

2. Biofiltration is resource-limited.  Resources for biofiltration as we use it include: 

Attachment space, as the bacteria involved are obligate attached growers and cannot metaboloze if not attached.  But providing more space then the colonies can used is futile. The limiting factor for bacterial growth for nitrification is energy food, not space for attachment.

Water flow: Water delivers O2, energy food, and the many other dissolved nutrients required for growth. The most successful colonies with be where there is attachment space with good flow but protected from silt, mulm, debris which could smother the colony.  Normally we set out filters to provide this space and protected flow.  If we do not, biofiltration bacteria will still establish wherever they can in the tank that these resources are available. We just make it easy for them to be mostly in one spot of our choosing and for our convenience.

Energy food: For our biofiltration bacteria, this is ammonia for one group, nitrite ion for the other group.  Production of ammonia in our tanks is limited to and by the fish's metabolism, the fish's solid, semi-solid, and liquid wastes in addition to the ammonia the release through their gills by simple diffusion and active transport, plus the sum of all the "lower" forms of life in the tank - infusoria and worms, copepods, bacteria and fungi, etc. - all of the invisible to barely visible to reclusive life forms in the tank.   All contribute to total bioload, but the largest factors are the fish themselves and the food that we add for them.

Th net of this is that If you have a functional bifiltration substrate, why change it?  If it is because you see another format to be "better" in some way, fine, feel free.  But make the the change slowly and with care that you do not remove too much at once.   

3.  Denirification: What is the point?   Bacterial denirification is more common than most folks realize, but does not IMHO in any way make our tanks "better"  It does not, repeat, does not increase the carrying capacity of our tanks.  Yes, we use nitrate production as a crude measure and indicator of  pollution , but that is only because we can measure it easily.  It has value to us only so long as we realize that it is not more a part of pollution, and selectively removing nitrate does nothing for all the other pollutants and imbalances in the water. If you remove nitrate alone, the only thing accomplished is to remove our best measure of pollution.   What about heavily planted tanks?  Tanks with functional denitrifiation deveices?   We punt - usually doing the same partials that we would do on the same tank without plants or such devices.  If your biloads are so heavy that you must do 2 50% partials weekly, recognize that fact and do the partials.  Don't waste your time and money kidding yourself that denitrification makes the cleaner and healthier.  To the best of my knowledge no one ever quantified total pollution, and without that it would impossible to quantitate how much of that total pollution and imbalance is represented by nitrate ion.

But also recognize that that tank, as with any heavy load high demand system, is fragile.  Such tanks are prone to collapse, not physical collapse, but biological collapse.  They crash.  Crashes are hard on livestock, and on their owners.   When you go past 50% partials weekly for any but the most demanding and delicate critters, it may be time to re-evaluate your goals.

Off soap box, return to normal programming.

[Taurus]

 

3.  Denirification: What is the point?   Bacterial denirification is more common than most folks realize, but does not IMHO in any way make our tanks "better"  It does not, repeat, does not increase the carrying capacity of our tanks.  Yes, we use nitrate production as a crude measure and indicator of  pollution , but that is only because we can measure it easily.  It has value to us only so long as we realize that it is not more a part of pollution, and selectively removing nitrate does nothing for all the other pollutants and imbalances in the water. If you remove nitrate alone, the only thing accomplished is to remove our best measure of pollution.   What about heavily planted tanks?  Tanks with functional denitrifiation deveices?   We punt - usually doing the same partials that we would do on the same tank without plants or such devices.  If your biloads are so heavy that you must do 2 50% partials weekly, recognize that fact and do the partials.  Don't waste your time and money kidding yourself that denitrification makes the cleaner and healthier.  To the best of my knowledge no one ever quantified total pollution, and without that it would impossible to quantitate how much of that total pollution and imbalance is represented by nitrate ion.

But also recognize that that tank, as with any heavy load high demand system, is fragile.  Such tanks are prone to collapse, not physical collapse, but biological collapse.  They crash.  Crashes are hard on livestock, and on their owners.   When you go past 50% partials weekly for any but the most demanding and delicate critters, it may be time to re-evaluate your goals.

Off soap box, return to normal programming.

Thanks for changing my focus on the big 3, ammonia, nitrites, and nitrates. Nitrates are not a measure of total pollution.

By biological collapse or crash, do you mean a sudden drop in pH, or acidification that kills the biofilter? I thought frequent partial water changes and thorough gravel vacuuming prevented that?

Would I be wasting my time and money by changing the biomedia in my filter to something that claims to be more efficient?

My goal has not changed..and that is to provide a healthy environment for the tropical fish that I enjoy watching and caring for. That is the reason for my questions and airing of these issues in public forum. I'm grateful there are many individuals here that have many more years of experience than I that can guide me.

[russ]

This one is heading to the library upon its climax.

[RTR...Grumpy Ole Fogie]

No, pH crash is just one of many forms that crashes can take.  OTS can be another, and so is NTS (old and new tank syndromes).  Crash just means that a tank that appeared to be functioning stops doing that.  The water may smell and be awful, the fish may be belly up , plants that were green yesterday are now slime or brown or both.  Surviving fish may be gasping at the surface or washed-out looking, sitting on the bottom or hiding as much of themselves as possible.  Generalized biological collapse is one form, a specific trigger resulting in collapse is another set - O2 lack from filte/pumop failure, electrical outage, bofiltration failure from any of multiple causes, heater failures in chilly rooms, AC failure in closed hot ones.  An almost endless array of horrible fates is available to us, but most are avoidable and (thankfully) rarely seen.  But the harder you drive any system, the greater the chance of something going wrong - and when one prop breaks, there is a spreading cascade of failure.   If a single pump failure can result in inadequate oxygenation, then the fish will suffer and may die, the biofilter will suffer from increased or even load but with lower O2 to operate so biofiltration drops sharply, further stressing the fish, the substrate stagnates and starts shifting to anoxia to deep anoxia, of from merely being anaerobic - pumping out things that are more toxic than ammonia and nitrite with not enough O2 available to oxidize then into safer forms - the landslide is full race downhill and the tank is effectively dead.  Our micro-ecologies are remarkably resistant, resilient, and adaptive. But they are so only as long as you are aware of the limits of our technology and of the systems we suoport with it.  If you drive in the slow lane and behave, you and the car get there.  If you hod-rod through the fast lanes with the tach red-lined all the way and play daredevil every time you get on the road, your and your car will likely have a much shorter history.  That does apply to tanks as well.  There is always a  division between you can do, and what you should do. 

[Santafebites]

And yes, I've read that adding plants wouldn't be of that much help because in lowering nitrates. I'll be testing daily for nitrates for the next week to see if the level approaches 20 ppm or higher.

I am confused by this quote, plants do help to absorb nitrates, no?

[Debra]

Melissa, (this can be deleted later)

Taurus has too many fish in too little water. The answer is really simple. Get rid of some of the fish. Plants simply won't solve this problem because the tank is overstocked.

HTH (and again, this can be deleted later)

[RTR...Grumpy Ole Fogie]

Santafebites  - the general case would be the same as denittification by any means (planted tank, algae- or veggie-filter, plenum, coil denitrator, microporous media, etc.).  A specific reduction in nitrate by any or all of those techniquess is  not improving water quality as it might be suggested by the reduction on nitrate-alone, as all the other pollutans are still there but are now undtectable or less detectable.  When any nirtrate-only reduction technique is practiced, measures of remaining nitrate levels have zero implications about water quality.

But yes, healthy, actively growing plants do reduce nitrate levels in a tank.  How much they reduce all the other pollutants is unknown.  They also make no overall corrections in other mineral imbalances, but may well increase those.

My veggie-filtered tanks do show lowered levels of nitrate than the did prior to their addition to the set-up, but that is not their primary function.   Their primary function is most often to supplement dark-cycle oxygen levels such that they do not show the usual dark-cycle reduction in O2 content, and frequently to increase the water volume in the system; only secondarily are they there to even out the nitrate levels between partials.  Partials on those systems are as with any other nitrate-reduction tank setup - purely arbitrary, based on total volume, not at all or in any way based on any parameter readings.

HTH

[Taurus]

LOL...I'll agree I may be pushing my stocking limits. But I won't agree with the statement that "my tank is over stocked, get rid of some fish."

OTS comes from tank neglect or lack of proper maintenance. Consumer grade test kits indicate my water parameters are in check (0 ammonia, 0 nitrites, 5 ppm nitrates, pH 6.8). Tank and filter maintenance are regular.
My fish show no signs of stress, no disease, no parasites. Lowering the depth of my gravel will allow me to vacuum it more thoroughly. I will cut back on feedings.

If a twice per week 50% water change is truely necessary, then that's the pattern I will follow. And it's fairly obvious that there is very little experince here with use of Eheim Pro Substrate or Seachem Matrix in an AC HOB filter because there has been little to no feed back on either product.

I will use the nitrate tests and pH as my guide because these parameters are good indicators of what is happening with my water quality.

[Sully]

Tank is overstocked.  That easy. 

Pristella maxillaris: grows to 1.5".  7.5" total fish length.
Rasbora heteromorpha: grows to 2"  26" total fish length.
Corydoras aeneus: grows to 3". 12" total fish length.
Oto: Grows to 2" 2" total fish length.

That is 45.5" of fish length in a 20-gallon tank.  Even by the 1" guide (which is probably applicable here) you have 2.25 times the maximum recommended stocking load.  Other variables come into play regarding room to swim for schooling species.  Those come out that once again, you are overstocked.

Then you consider 1 oto in an unplanted tank--very poor stocking decision.

Not enough gallons or space for the fish in the tank.  Coupled with inappropriate decor.  Now that the issue of overstocking is done and solved, the easy answer is to reduce feeding like RTR and Mary said. 

Then measure what happens with the nitrate level.  That is the answer to your question since you don't think you have too many fish (a significant factor in bio-load pollution).

After that you are stuck with water changes.  Not a bad thing.  After that consider another tank to eliminate your overstocked situation.  Those fish are in for a tough haul in that tank.  Probably looks good--but looking good does not make it good for the fish.

[RTR...Grumpy Ole Fogie]

Don't be too hasty on your conclusions.  I confess to over-abstraction - I thought that I had already dismissed microporous bacterial media in earlier posts on this thread, but I neglected to mention that both the media listed are exactly that, microporopus media.

Yes, microporous media can function for some period as both nirification and denitrification biomedia, and that does include the twp products specified.  Microporous media will develop facultative and fully anaerobic bacterial colonies in their internal pores, perhaps even deep anoxia-dwelling forms -under the same conditions as are seen in DSB (deep sand beds) and plenums (which will not or should not show deep anoxia) or in undisturbed sand substrates in any tank.  In tank substrates anoxia increases with depth. The slope of that curve depends on the particle size, with large particles O2-levels drop slowly (most gravel not clogged by mulm), while with smaller particles O2 levels drop off more rapidly.   Microporous media provide the same function by variation in average diameter and the total length of the channels  - an oxygen gradient develops.  The denirtification bacteria we host are anoxic/anaerobic - oxygen is toxic to them - but they are not critters of the deepest anoxia conditions.  There will be many areas which provide their desired conditions. 

However, there are no mechanisms for disposing of spent biofilms in microporous media.  Surface bacterial colonies such as our familiar nitrification bacteria, grow constantly.  They eventually over-grow (atop their kin) and the mass loses its attacment and is swept away by the current.  Think of it as flaking and peeling paint on a house exterior, but on a microscopi scale.  Fine, tiny sections of biofilm are lost, but fill in rapidly from the edges or by tinier bits of biofilm left in place.  Colony size is stable within ~one population doubling overall, but some area are overgrown and some are newer by fill-in.  Fine, that works for a dynamic balance - pretty standard for biological populations at any scale.  Those internal channels in the biomedia have zero current, only diffusion functions to transfer materials.  Brownian motion can move some biofilm fragments, but is ineffective for dead pouplation clearing.  Those micochannels are blocked more and more by their developing and developed biofilms .  That biological growth itself slows and eventually block the diffusion processes going on.  The microchannels become blocked and move to deep anoxia.  The denitrification bugs die.

All of that is not a fast process.  The microporous media requires regular and routine replacement wit fresh material.  So by periodic replacement of 1/4 or 1/3 the media volume, the process may be be maintained indefinitely. 

Then you must judge the net worth of the value of that process to you.  To me it is an interesting and challenging area of study, and I have spent a good bit of time playing with those techniques.  But the result of that study was that I see no value whatsoever to the hobbyist in using such techniques, as i explained more fully before,  the result is partial, and with miroporous media not free or low cost, removal of one particular pollutant  and unfortunately the only pollutant that we can easily measure to guesstimate the overall water quality. To me it is spending money and time in order to make you life more difficult.  To me that is shooting yourself in the foot.

Sully has already chimed in on the fact that the tank is in fact overstocked, with which I strongly agree.  I will only add that in the event of a power out age, you will have dead fish without much attention from you.

HTH

[Taurus]

Coupled with inappropriate decor. 

LOL..care to expand on this Sully?

[Taurus]

Thank you RTR...now I understand why microporopus media MAY not be such a good thing.

[Sully]

I won't go too far with it.  I will just do the easiest comment.  An unplanted tank.  An oto.  They feed on roots of live plants.  They are a plant cover and wood cover dweller.  They live in what is commonly called a "vegetative zone".  That is the type of fish they are.

The Pristella is a fairly forgiving fish.  They do best color wise with a dark substrate and subdued lighting--lighting often achieved with good plant cover.

Rasbora heteromorph.  Very simply stated.  They are best kept as residents of planted tank with (once again) subdued lighting.  Lighting that is often achieved by a lot of surface level vegetation.  They too are a resident of vegetative zones. 

Cory's are into soft and/or sandy substrate.  They have very delicate barbels that are often damaged on gravel substrate.  They do not dig well in gravel.  Might be why even with the cory's you had a a problem with uneaten food in the substrate.

You have fish that do best in a tank that is different than that which you have created.  The key to reduce fish stress (and subsequent disease), achieve best coloration, and have fish live to and beyond their wild life span is to decorate the tank in a fashion that is conducive to their needs.  With the schoolers that are water column feeders you can get the desired effect with a lot of fake vegetation and the appropriate diet. 

When people come to this section of the board to solve fish health problems their is a very easy formula to use when trying to figure out the best short and long term solutions. 

The first step is the step you are concerned with--water quality.  The parameters of basic water chemistry.

The second step is to look at stocking levels and how the species are stocked.  You obviously have a problem with overload and what i would call inappropriate stocking of the cory's and the oto.  You need more of each species and you tank cannot support the population requirements as aresult of the overstocking already encountered.

The third step is to look at the decor of the tank.  Is it set up in a way that is conducive to long term health--yours is not.

And there is an overall dynamic called tank maintenance--water changes, gravel vacs, filter cleaning....That is often included in the water quality area--but while influencing water chemistry--it is not exclusively a water chemistry issue.

If you had a disease problem you would get the basic info on how to treat the symptom of the problem.  Whether it would be bacterial or parasitic.

The second bit of advice you would get is to thin the herd.  You would be told that the tank is seriously overstocked in combination with inappropriate stocking.

The third bit would be to change the tank decor.  Points two and three would be to establish an environment conducive to long term health issues and stress reduction. 

Okay--I went further than I planned.  In a nutshell the tank is a disaster waiting to happen.  Your issues go far beyond nitrate level and water change frequency.  You opted to laugh off the comments others made.  They were right.  They may not have been as blunt or elucidated their concerns.  But they were right.  We could get into a discussion of how DOC's and decaying foods significantly increase the bacterial and parasitic loads.  We could discuss overstocking from the angle of host presence.  With that number of specimens viral, bacterial, and parasitic disease are in 7th heaven.  They can multiply quickly to the point that pathogens overwhelm the tank faster than the hobbyist can react.

Good Luck.