Tropical Fish Keeping - Aquarium fish care and resources

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car0linab0y 04-14-2010 10:23 PM

First Planted (low-tech), Newb Question
I know it's recommended not to have surface agitation with a planted tank, but I've also read that plants CONSUME O2 rather than producing it during the dark half of the photosynthesis cycle. I just planted the tank today, so the roots haven't had time to anchor. Would it be wise to run my HOB (throttled down) when the lights are off? I was going to have a powerhead with a sponged suction as the only mechanical filtration, but my little ebay china made powerhead will blow the glosso's out of the gravel, possibly some of the larger plants too. The HOB just has mechanical filter, no carbon or bio media.
Tank: 65g - 36Lx18Hx12D (I think, I know it's 36L)
Fish: 6 yellow barbs, 7 sword tails, 2 fry
Plants: Amazon swords, Glosso's, Giant Hygro, Lobelia, Blyxa

bettababy 04-15-2010 01:11 AM

First and foremost, the amount of surface agitation or circulation in a planted tank largely depends on the species of plants. Some plants can't handle it, other plants can't live without it. Another determining factor is location of the plants vs the output from the filter where the strongest amount of flow will come.

I have a house full of planted tanks, all run hang on filters except my 29 gallon biocube which runs a sump system in the back & 75 gallon with canister,. You can check out the photos in my aquariums section by clicking on my name. And yes, I do run carbon in some of my filters, others I have only biomedia in them.

And you are correct about plants consuming O2 during dark hours. Again, the amount they consume/use depends on the species of plant, temp of the water, amount of light during the day, how healthy the plants are, what other nutrients they are taking in, and water chemistry.

Have you yet run this tank during dark hours without a filter? If so, what kind of results have you had thus far and how long has that gone on? If you've done it successfully long term, I would say if its not broke, don't try to fix it. If you either haven't done it yet or have seen a decline in conditions in your tank, then I would say there is no reason not to give it a try if you are keeping plants that can handle it, and as long as delicate plants are not caught directly in the water flow from the filter. Some filters have a stronger outflow than others... that should also be taken into account.

Based on the tank info in your signature, you have a 30 gallon breeder tank. (this is calculating dimensions listed.. and so you have the proper info in the future 30 gallon [US, liquid] = 113.562 353 52 liter)

For the plants you are keeping, if you desired to run a hang on filter just for oxygenation purposes, work with something rated for a 10 - 20 gallon tank, not 30 gallons. This will greatly cut the water flow for those plants that are more vulnerable to the outflow pressure, and be sure the filter is in a location so it is not putting water flow directly on the plants. This may take some time and a bit of experimenting, but shouldn't be too difficult to achieve.

car0linab0y 04-15-2010 11:52 AM

sorry, wrong tank dimensions... 36Lx18Wx24H
I just put the plants in yesterday afternoon, so I haven't had a chance to see what kind of effect not running the filter at night has. I went ahead and ran it last night to make sure my fish didn't asphyxiate.

Austin 04-15-2010 01:56 PM

The plants should produce enough oxygen during the day to account for the fish night and day, and the plants at night.

I haven't seen this as a problem in my 29g tank yet. I have a small internal filter.

You'll also be able to tell before it hurts you fish if they are lacking oxygen.

Promelas 04-15-2010 05:03 PM

Just out of curiosity I have a question to add to this topic. I've noticed that people discuss the o2 consumption during the night from time to time and was just wondering if this is in reference to the Calvin cycle part of photosynthesis (aka dark cycle)? The name is somewhat misleading since it doesn't only happen at night, just that it doesn't need light for the reaction. I haven't had to study the nitty gritty details of photosynthesis for some years and I don't remember it all so I was just curious what part of the cycle uses the o2, or if it's independent from photosynthesis entirely.

La Reina 04-15-2010 09:44 PM

Cellular respriration is what plants do at night, it is also what all animals do. It is a "dark" cycle because it does not require sunlight to "crack" glucose down to CO2 and H2O (and ATP for those bio geeks.) The Calvin-Benson cycle , I beleive, is the syntesis of glucose which requires light.

Promelas 04-15-2010 10:22 PM


Originally Posted by La Reina (Post 363630)
Cellular respriration is what plants do at night, it is also what all animals do. It is a "dark" cycle because it does not require sunlight to "crack" glucose down to CO2 and H2O (and ATP for those bio geeks.) The Calvin-Benson cycle , I beleive, is the syntesis of glucose which requires light.

The "dark" cycle and the Calvin cycle are the same thing, and the Calvin cycle does not require light. The "light" cycle generates ATP which is used for the non-light driven reactions.

Quick edit: I understand that cellular respiration happens in plants, as it does with us, but I've just never seen any scientific article or text that states that this only happens at night. Any text I have ever read has said this happens during the day as well as at night. If you would happen to know any sources that says it happens solely at night I'd be more than happy to read it!

Mikaila31 04-16-2010 01:03 AM

I believe respiration happens very limited throughout the day. The issue is that cellular respiration is less efficient than photosynthesis, nature is focused on energy conservation. IMO it would make little sense to have a lot of cellular respiration going when photosynthesis can.

Promelas 04-16-2010 07:45 AM

I'm a little confused as to what you mean when you say photosynthesis is more efficient than respiration since they're basically two different processes entirely. The point of photosynthesis is to create glucose that can later be broken down to generate ATP by cellular respiration. The benefit of photosynthesis is that the ATP necessary to create glucose comes from the electron flow created by "exciting" the electrons using light within the chlorophyll molecules. If plants weren't able to harness light they would be stuck in a cycle of using ATP to make glucose and then using glucose to make ATP without any real net gains in ATP.

redchigh 04-16-2010 11:59 AM

Plants consume miniscule amounts of O2 constantly. 24 hours a day, 7 days a week.

They convert CO2 to O2 in vast amounts, as a product of photosynthesis. I was worried about that for a while, but there's no need to worry- you're overthinking it. :)

They produce WAY more 02 during the day than they consume, so still more than enough for your fishes and bacteria.

As far as surface agitation though, a little won't hurt. I have a HOB filter in my 10G-
I don't think my plants mind. :)

I think it's the amount of aeration to worry about- a HOB filter, or minor water movement is OK, maybe even good for some plants.
However an airstone is a no no.

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