Day time flow and Night time
- Thread starter AlexT
- Start date
Hello Alex. The filter flow should be low enough that your small fish don't get tossed around the tank. I would keep the flow moderate, but steady. The real issue for such a small tank is your water change routine. Even though the fish are small, you have overloaded the tank. Your water change routine should be equal to the number of fish you have in it. If the tank was mine, I'd make plans for setting up another larger tank and transfer half the fish to the new tank. If this isn't an option, then you need to remove and replace at least half the tank water every three to four days and feed just a bit every other day. Even very small fish can generate quite a bit of waste and it needs to constantly be removed so toxins can't build up and harm your fish.
The number of fish you have in 20 gallons of water, I have in my 55 gallon tank.
10 Tanks (Now 11)
The number of fish you have in 20 gallons of water, I have in my 55 gallon tank.
10 Tanks (Now 11)
I consider the flow in the video good for daytime. You say you adjust it for night, I am not sure this is needed. How much stronger is it at night?
I know you are relatively new to this, so I'll do a bit of a summary. Surface disturbance provides the exchange of gasses, oxygen and CO2. A few decades back, the thinking was that minimal disturbance during the day was better because it would not drive out the needed (for the plants, this is a planted tank we are talking about) CO2. About a decade ago, planted tank sources began to suggest that this was a mistaken assumption, and more disturbance was better at retaining CO2. I was a member on a few planted tank forums then, and I asked about this, but absolutely no one could provide any evidence that it was actually true. To me, this is like the fads for laterite, or kitty litter substrates, etc...basically nonsense.
Plants, fish and some bacteria species all respirate continually, taking in oxygen and giving off CO2. This occurs day and night. With no plants, it would remain basically the same day and night, and good surface disturbance would be more advisable to ensure good oxygen and less CO2. With plants, we have a need for more CO2 during daylight. Plants cannot photosynthesize unless the light intensity is adequate for the specific plant species, including the spectrum. If all nutrients needed are available with the light, photosynthesis will occur full-out. When something is no longer available, photosynthesis slows and may even stop. During photosynthesis, plants need carbon, and most obtain it as CO2 from via the leaves. Some plants will also use bicarbonates. Vallisneria for example is especially effecient at this, which is why it is good in water with a higher GH. Vallisneria is native to the African rift lakes, about the hardest freshwater in the hobby. Plants produce oxygen as a by-product of photosynthesis, and they release it as waste primarily through the roots. When one sees "pearling" from plant leaves, that is excess oxygen being released. I sometimes see this after a water change; the dissolved CO2 in the fresh water provides more carbon for the plants, so much so that they go into overdrive and hence the oxygen. This is minimal, but in high-tech planted tanks it is very common.
As I said, photosynthesis will continue full-out until something runs out, and for most of us this is carbon. We rely on natural CO2 from the decomposition of organics in the substrate, and this can produce quite a lot. Once you have the light balanced to this CO2, and assuming other nutrients are available, plants will thrive but algae is thwarted. But once the balance is off, algae has an advantage because it is not fussy over nutrients or light. One reason floating plants grow so fast and are thus such excellent water purifiers is because they have the aerial advantage over submersed plants: the leaves on the surface can take in CO2 from the air, which for the plant is four times faster than assimilating CO2 from the water.
During darkness, the production of CO2 continues just as it does during the day. But plants cannot use it without light to drive photosynthesis, so the CO2 builds up. We want this, because it will then feed the plants the next day. But, there is always the danger the CO2 will build so much it will harm the fish. I experienced this in my cory tank. In the very early morning, their respiration was very rapid, but during the day is was normal. I was able to figure this out, and I increased the surface disturbance. Problem solved, no more respiration issues. I simply had to quicken the gas exchange enough to settle the fish, while still ensuring enough was being saved for the plants to use next day.
The surface disturbance I see in your video is fine for the day, and may be OK for night too. Tomorrow, get in front of the tank in a chair when the tank light comes on, and observe the respiration rate of the fish. Cories are good indicators of this, since they are down at the substrate level and even with their normal bumbling around are not too active to be able to see respiration. Make sure they are not feeding at that time. Any activity including feeding will increase their respiration noticeably, so that doesn't solve things re the gas exchange.
Ask me any questions if anything here is not clear.
I know you are relatively new to this, so I'll do a bit of a summary. Surface disturbance provides the exchange of gasses, oxygen and CO2. A few decades back, the thinking was that minimal disturbance during the day was better because it would not drive out the needed (for the plants, this is a planted tank we are talking about) CO2. About a decade ago, planted tank sources began to suggest that this was a mistaken assumption, and more disturbance was better at retaining CO2. I was a member on a few planted tank forums then, and I asked about this, but absolutely no one could provide any evidence that it was actually true. To me, this is like the fads for laterite, or kitty litter substrates, etc...basically nonsense.
Plants, fish and some bacteria species all respirate continually, taking in oxygen and giving off CO2. This occurs day and night. With no plants, it would remain basically the same day and night, and good surface disturbance would be more advisable to ensure good oxygen and less CO2. With plants, we have a need for more CO2 during daylight. Plants cannot photosynthesize unless the light intensity is adequate for the specific plant species, including the spectrum. If all nutrients needed are available with the light, photosynthesis will occur full-out. When something is no longer available, photosynthesis slows and may even stop. During photosynthesis, plants need carbon, and most obtain it as CO2 from via the leaves. Some plants will also use bicarbonates. Vallisneria for example is especially effecient at this, which is why it is good in water with a higher GH. Vallisneria is native to the African rift lakes, about the hardest freshwater in the hobby. Plants produce oxygen as a by-product of photosynthesis, and they release it as waste primarily through the roots. When one sees "pearling" from plant leaves, that is excess oxygen being released. I sometimes see this after a water change; the dissolved CO2 in the fresh water provides more carbon for the plants, so much so that they go into overdrive and hence the oxygen. This is minimal, but in high-tech planted tanks it is very common.
As I said, photosynthesis will continue full-out until something runs out, and for most of us this is carbon. We rely on natural CO2 from the decomposition of organics in the substrate, and this can produce quite a lot. Once you have the light balanced to this CO2, and assuming other nutrients are available, plants will thrive but algae is thwarted. But once the balance is off, algae has an advantage because it is not fussy over nutrients or light. One reason floating plants grow so fast and are thus such excellent water purifiers is because they have the aerial advantage over submersed plants: the leaves on the surface can take in CO2 from the air, which for the plant is four times faster than assimilating CO2 from the water.
During darkness, the production of CO2 continues just as it does during the day. But plants cannot use it without light to drive photosynthesis, so the CO2 builds up. We want this, because it will then feed the plants the next day. But, there is always the danger the CO2 will build so much it will harm the fish. I experienced this in my cory tank. In the very early morning, their respiration was very rapid, but during the day is was normal. I was able to figure this out, and I increased the surface disturbance. Problem solved, no more respiration issues. I simply had to quicken the gas exchange enough to settle the fish, while still ensuring enough was being saved for the plants to use next day.
The surface disturbance I see in your video is fine for the day, and may be OK for night too. Tomorrow, get in front of the tank in a chair when the tank light comes on, and observe the respiration rate of the fish. Cories are good indicators of this, since they are down at the substrate level and even with their normal bumbling around are not too active to be able to see respiration. Make sure they are not feeding at that time. Any activity including feeding will increase their respiration noticeably, so that doesn't solve things re the gas exchange.
Ask me any questions if anything here is not clear.
Brilliant, thanks Byron. Loved reading every word of that. I was aware of surface agitation driving off CO2 and the impact of excess CO2 on fish (well, in my mind lack of available oxygen). When I had a fully planted and thriving tank years ago, I quickly noticed a pattern of some (not all) fish gulping in air at the surface first thing in the morning. I quickly worked out from reading up, it was related to the changed dynamic between oxygen and CO2 over night. I added an internal filter for extra surface agitation, that I only switched on at night (I stuck some media in it, but I obviously wasn't using it for bacteria reasons). Even back then, years ago, I always had my ammonia and nitrite test kits. I didn't know so much about pH, KH, and GH.
I did know in my mind (right or wrong) that excess surface agitation would wipe out or reduce my natural CO2 that was available. I knew plants needed CO2. It was all the rage to have CO2 set ups which i couldnt afford.
It was in this tank that my Vallis was awesome, no surprise. I am still living in the same place now, GH 16 London UK rock hard tap water.
Also in the previous 4 foot tank, it was heavily stocked / overstocked, but I never saw even the slightest hint of ammonia or nitrite (and I am a testing addict) and my nitrate was never above 10 despite tap water of 30ish and an overstocked tank. I was good on water changes, so even with 30 Nitrate going back in from taps, I assumed my tank readings of 10 nitrate were due to thriving plants?
With regards to water agitation at night, I'll increase only very slightly tonight or i will worry. I will monitor in the morning and report back. If I see no respiratory distress in the morning, I will leave the flow 24hrs as you saw in the video.
I find small characins also a good indicator of available oxygen as they tend stay more still, and pant, even if they don't go to the surface.
Thanks again.
This is another debatable point, plants using or not using nitrate.
Most aquarium plants prefer ammonia/ammonium, and will ignore nitrate if the ammonia/ammonium is in balance with all other nutrients and the light. They will not switch to nitrate (or nitrite) under normal circumstances (low-tech, natural method planted tank) because chances are the light and other nutrients (esp carbon here) will not be sufficient. And it takes plants about 24 hours to change gears. And, when they do, they have to then spend considerable energy changing the nitrate back into ammonium so they can use it. So, it is not surprising that they tend to ignore nitrate. [In high-tech systems it is very different.]
Diana Walstad goes into all this is great detail in her book Ecology of the Planted Aquarium, citing numerous scientific studies.
Also, there is denitrification. Bacteria that use nitrate to create oxygen. And, there is the change from nitrate to nitrogen gas that then escapes back into the atmosphere at the surface.
How ironic. Had my first power cut over night. Something in the house tripped out the fuse box. First time in years. Fish are all good. No gasping or respiratory distress. Not sure how long the power was out. Could have been anything from 30 minutes to 6 hours.
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