Lack Of Oxygen

[sumocopter]

Hi all,
 
I have had some problems recently with seemingly a lack of oxygen in my tank.  After my last water change, and filling up a little more than normal, I lost my surface disturbance from the spray bar.  ALL the fish were lying on the bottom or gulping at the surface the morning after, dropping the water level to give some surface movement and putting 2 airstones in helped them all pull through - some kind of miracle!
 
Previously I have had problems with possible nitrite poisoning, an improved filter and that is no longer a consideration.  BUT I am still generally low on oxygen.  After my last incident I invested in an Oxygen testing kit.
 
Tank info
4'x2'x2' - 9 discus, 15 lemon tetra, 8 bronze cory, 3 common plec - bogwood and amazon swords (that don't do very well....)
Ammonia 0.25
Nitrite 0
Nitrate 10
PH 7.6
KH 3
GH 14
 
O2 2mg/l
 
Does anyone have any experience of oxygen problems? How is best to boost the oxygen? Surely adding oxygen tabs to a tank isn't ideal or sustainable?
 
Thank for any help in advance.
 
Sumo

 

[Akasha72]

my knowledge on this is limited but as I'm here I'll see if I can help somewhat.
 
When you say you lost some surface movement from the spray bar - could this be a flow issue? Have you checked for blockages within the spraybar or filter pipes? Has the filter been cleaned recently? I'm presuming it's an external seen as you have a spray bar so have the pipes been cleaned recently? All these things can reduce the filter flow and then produce a lack of surface movement and then finally low oxygen levels within the tank ... it's a bit of a knock on effect. One thing leads to another.
 
Another reason for a lack oxygen could be down the tank temps. We are now in the summer months (most of us anyway!) and so our tanks are hotting up. Here's in the U.K we're having a bit of a heat wave and we're all having our tanks running slightly warmer than normal. This can have an effect of the amount of oxygen within the tank too. I'm currently running an air stone 24 hours a day in my tank as my flat is heating up a lot during the day and taking the tank temp with it.
 
I also note from your list of tank stats that you have a reading for Ammonia. This can also cause the fish to either sit on the bottom or gulp at the surface. I'd recommend upping your water changes to get the Ammonia reading down to zero and staying at zero.
 
I also can not leave this thread without mentioning those common pleco's. You will either need to upgrade your tank to around 8ft if you want to keep them long term. These fish can reach well over 2ft long and so they can not stay in a 4ft tank long term. The other option would be to re-home them now before they become a problem. Sorry to be the bearer of bad news where they are concerned

 
 
I hope I've been of some help and I hope you can sort the problems quickly 

 

[RRaquariums]

Setting aside any other things going on with your tank if you are just looking to boost oxygen levels I've found a small powerhead positioned at the top of the tank so it's causing a current across the whole top of your water is a good way to keep oxygen mixed in and the release of gasses from the water. If you pair an air stone with this power head it's even more affective.

 

[Ch4rlie]

You say have an improved filter and you have 0.25ppm of ammonia.
 
This kind of leads me to think, did you swap over the cycled filter media from the old filter to the new one?
 
This may be an ammonia spike if this is a new filter as the old filter would have had bacteria all over it inside the filter as well as inside the hoses etc, so you may have lost that amount of bacteria, hence the ammonia spike, but if you still have the cycled media in the new filter, the bacteria colony should quickly get back up to strength.
 
A fully cyced tank and filter should never give a reading for ammonia nor nitrite without any reason.
 
Do accept my apologies if I have read that wrong about your filter.
 
However, i concur with the above advice regarding the common pleco and the suggestions to boost air circulation in the water column.

 

[sumocopter]

Hi all,
 
Thanks for your replies
 
I am fully aware of the common plec issue.  The plan is to upsize when I move house, hopefully in the not too distant future.  I am afraid that a good few years ago i suffered an LFS 'no these won't grow too big'...they are now growing quite big!
 
The filter media was all moved to the new filter (Eheim 2080) at least 5 months ago.  Ammonia was 0.25 was today, normally 0.
 
The surface movement thing is definitely not to do with filter maintenance.  Flow is good, there were no issues before the water change, just dropping the water level so that the surface was disturbed sorted the problem after the water change (the two airstones were removed at the end of the day and all was fine).  The tank is at 29deg and has been so for months - thankfully there has been no change even with the recent lovely weather.  The pathologic lack of oxygen was definitely acute, it was solved by the appropriate action.  I am more concerned about the long term low oxygen levels so that I do not have to worry about this in the future.  I would rather not be teetering on the edge of 'just about enough' oxygen.
 
Sorry to bring this back to the oygen thing, but I am 100% sure that this is the issue, I am just not sure how I have arrived here or how to resolve it.
 
Cheers
 
Sumo

 

[Akasha72]

29 degrees is far too warm for all of your stock - the cories in particular. I'm surprised they are still alive at those temps. It needs to come down to around 25-26. I think you will find with a lower temperature the oxygen problem will fix itself

 

[sumocopter]

Thanks for your advice

 

[Ch4rlie]

Temperature in tank water has a direct effect on dissolved oxygen in the water.
 
Water will hold less oxygen the higher the temperature.
 
Now, most fish are not affected by this as long as they are kept in near temperautres ranges they were evolved to live in from their habitats, so therfeore they would be evolved to live in less dissolved oxygen.
 
A couple of things would happen when high temperature is reached in the aquarium, one is the amount of dissolved oxygen will fall. Second is the metabolism in the fish will rise as well as their need of oxygen.
 
This in turn will stress the fish, leading to be more susceptable to diseases and more likely than not, their lives wil be shortened. This is especially true of certain species like coryadoras, barbs and danios. They do not cope well with higher temperatures at all.
 
After doing a little research in finding out how much dissolved oxygen most tropical fish can cope with, a general rule of thumb seems to be around 5ppm or 5mg/l.
 
In normal tropical temperatures, around 24C / 75F the amount of dissolved oxygen is around 8ppm or 8 mg/l.
 
Then when you look at the amount of dissolved oxygen at 29C / 84F it is lower at around 7.5ppm / 7.5 mg/l.
 
That 0.5ppm difference can make a big difference to certain fish species as mentioned above.
 
So basically, your fish are gasping at the water surface is likely due to the higher temperature that is required. It is fine for discus but as for the tankmates, such as your cories and plecos, not so much.
 
This is why research is vital when choosing tankmates for certain fish species, temperature and compatibility is key.

 

[Akasha72]

thank you ch4rlie, you put what my poor tired brain couldn't tonight.
 
Whilst I know Discus prefer it warmer - much like angelfish too - it's too hot for the other fish. As you say, research is key. Sadly I didn't research angelfish enough and made it hard on myself. They would prefer it up around 27 degrees but that's too hot for my cories which is why I keep my tank at 25.5 (ish) ... I've tried to find the balance. It's not the best but it is the best I can do for now

 

[Byron]

I would not mess much with the temperature here.  You have nine discus, and the temp suggested for discus by the reliable sources is around 82F/28C, so you are only one degree C above which will not be a problem for discus.  As for the other named fish, the corys (the species here is bronze, presumably Corydoras aeneus) will not be comfortable and should be removed.  Lemon Tetra (Hyphessobrycon pulchripinnis) are at the top end of their range or a degree above (accepted range is 22-28C/72-82F) so this is going to cause issues for them long-term.  The pleco (assuming it is the "common" species Hypostomus plecostomus) should be OK, subject to what I will mention momentarily.
 
Quickly on the plants, this is quite warm for Echinodorus though there are likely other issues affecting the plants which we can explore if you like.
 
Obviously it would seem that the oxygen in the water lowered due to decreased water disturbance, so that should be easy to keep stable.  There should be some disturbance of the surface, especially in the area of the filter return, that should suffice.  Air stones and bubble wands can help, but not all of us like to see these devices operating so I would only resort to them in an emergency.  The warmer the temp, the more critical is water movement with surface disturbance, and it is easy enough to keep this present without too much current which of course the discus will not appreciate.
 
Now back to the fish and warm temperatures.  With a few exceptions, the temp range given for species by reliable sources is not meant as indicative that the species can manage long-term at either extreme, but will be best somewhere mid-range.  Dealing here with the high end of the range, this causes the fish's \metabolism to operate at much higher rates than it needs, just to maintain the proper balance of the physiology of the fish, the homeostasis it is called.  Think of it as driving your car uphill; it takes more gas (= energy) and effort to maintain the same operating speed as it would on level ground--and so it is with fish.  Warm blooded animals can somewhat deal with this, but fish cannot.  So one should always carefully consider a species "preferred" temperature (and other water parameters are important here too, for the same reason) and select species that will be able to function best in the given temperature.  You mention this temp having been set for a time, with no issues.  Unfortunately, there are issues, but we cannot usually see them until it is too late.  To keep the fish in the best of health, temperature is crucial.
 
Hope this is of some benefit.
 
As I was typing, Akasha posted, so I will just comment on the angelfish temperature.  Tank-raised angelfish (as opposed to wild caught) do not need warmth; they are fine at 76-77F/24.5-25C.  A slight increase might trigger spawning, but for general maintenance, you should not have issues.
 
Byron.

 

[Akasha72]

the increase due to the heat wave has indeed induced spawning Byron. They are preparing the spawn currently. Many thanks for you reassurance on the temp

 

[TwoTankAmin]

There are basically 0nly two reasonable ways to get O into a tank. One is surface agitation which facilitates gas exchange, the other is the use of live plants. An airstone does not put any meaningful oxygen into a tank from the bubbles rising, The bubble size is way too large and the contact time way to short. What an airstone does does is to provide surface agitation when the bubbles break the surface.
 
Nitrite poisoning does not cause a lack of oxygen, the nitrite gets into the blood and blocks it from holding oxygen. Thus, even in a well oxygenated tank the fish can suffocate due ti nitrite. The only thing I am aware of that will actually counteract the effects of nitrite already in a fish is Methylene Blue and this will stain a tank. However, one can effectively block the effects of nitrite by using chloride rather than water changes. Normally dealing with nitrite by blocking it or doing water changes is sufficient to allow fish to recover in 24-48 hours. the chloride is a less stressful solution.
 
Because you showed some ammonia level it is possible you had some nitrite as well which affected the fish. Your water change ameliorated this and gave the fish time to work the nitrite already in their system out. I think the lack of surface agitation exacerbated things. Ammonia can also affect fish respiration.
 
Next many water conditioners are reducing agents which will act to lower DO levels when they are first added. this means when you might test for O will matter. And it is not just the dechlors etc. that are reducing. So too are things like liquid carbon supplements such as Excel.
 
Finally. I am not sure how trustworthy hobby O test kits are, but 2 mg/l of DO is nowhere near sufficient in a tank for most species.

What is Oxygen Depletion?
Oxygen depletion refers to low levels of DO and may result in fish mortality. A concentration of 5 mg/L DO is recommended for optimum fish health. Sensitivity to low levels of dissolved oxygen is species specific, however, most species of fish are distressed when DO falls to 2-4 mg/L. Mortality usually occurs at concentrations less than 2 mg/L. The number of fish that die during an oxygen depletion event is determined by how low the DO gets and how long it stays down. Usually larger fish are affected by low DO before smaller fish are.

from https/edis.ifas.ufl.edu/fa002
 
For those of you who are curious, here is a paper which compared different types of tests kits for various parameters: Ammonia, Nitrite, Nitrate, pH, DO and Temp. They tested several factors. They compared test results from 5 different types of testing kits or meters using known solutions. They also compared how 4 or 5 different users' results varied when they all used the same test method/kit.
 
Testing your Aquaponic System Water: A Comparison of Commercial Water Chemistry Methods
https/www.google.com/url?q=http/www.ctsa.org/files/publications/TestingAquaponicWater.pdf&sa=U&ei=F2ihVbS6Nonw-QH_iZHYAg&ved=0CD8QFjAKOAo&usg=AFQjCNFAW0Q0nHSX6q-WJxXODbOIAfgxLQ

 

[sumocopter]

Wow, thanks everybody!  It looks like I'm making sure that surface agitation is always present, dropping the temperature a degree or two and thinking about rehoming those corys.
 
Thanks for your help.
 
Sumo