what could be the problem?

[hulu]

I got a 20G long, with about 10 fish and heavily planted. For some reason, I can not grow didiplis and a few other plants (like Blyxia) well. Stem rot seems to be one major problem---a healthy plant would suddenly rot and float. intially I thought something is missing in the tank, but most of other plants is growing well. Further more, last weekend, because of a busy schedule, I skipped one water change, and did NOT add any ferts for the following 4 days. To my big surprise, everything in the tank is growing BETTER than before! I am confused.

Here is my schedule:

Tank: 20G long
Light: 96W 10 hours
CO2: DIY, 4 bottle, 2bubble/sec, DIY reactor with venturi
Filter: Eheim 2215
tap water: very soft, hardness ~20ppm
water change: weekly, 50%

Barr's GH booster: 2tsp, when changing water
KNO3: 3/8 tsp, 3X /week
KH2PO4: 1/8 tsp, 3X /week
CSM+B: 1/8 tsp, 3X /week
iron: seachem, 1ml, 3X /week

The leaves of my nasaea also has been small and curved with my regular dosing. However, after the 4 days without adding anything, they are extended, and much healthy! What could this mean?

Thanks for your help.

 

[Tom Barr]

Try upping the CO2.

Those two plants do poorly without good CO2.
Water's soft, got light, got nutrients etc.

You likely only need maybe 1/2 the amounts you are dosing.
DIY is the biggest issue, you have to keep up on that.
And that goes back to CO2.



Regards,
Tom Barr

 

[VaughnH]

A 20 gallon tank would need closer to one bubble per second than one bubble per minute, so you are very likely way low on CO2.

 

[hulu]

A 20 gallon tank would need closer to one bubble per second than one bubble per minute, so you are very likely way low on CO2.

Sorry, a typo. Thanks for pointing that out to me. My bubble rate is 2 bubbles/second, made with 4 connected DIY bottle.

 

[hulu]

Try upping the CO2.

Those two plants do poorly without good CO2.
Water's soft, got light, got nutrients etc.

You likely only need maybe 1/2 the amounts you are dosing.
DIY is the biggest issue, you have to keep up on that.
And that goes back to CO2.



Regards,
Tom Barr

Thanks for the reply, Tom.

I checked my CO2, it has been quite steady for a long time, 2 bubble/sec (sorry, not /min, it was a typo, thanks Vaughn pointing out to me). Plants are pearling like crazy. I had riccia stones everywhere, they start pearling significantly 1 hour after the light is turned on. The problematic plants I mentioned are close to these riccia stones. As Riccia are good CO2 indicater, it seems to me CO2 should not be a problem.

Back 3 months ago, Blyxa has been growing like crazy in the same tank --- at that time I had to sell a lot to my LFS. The only difference is back then , I did not add GH booster, and my CO2 was only 1 bubble/sec. But back then my HC was growing poorly. Things are oppsite now, my HC are spreading green and thick, with contrast Blyxa are almost gone.

Could this be allelochemicals secreted from one plant inhibit the other, as Diana pointed out in her book "Ecology of the planted aquarium"? Or are there some ferts reaching toxic level in my tank? That would explain when I forgot to add ferts for 4 days, those plants recovered a little bit.

Please let me know what your thoughts are. I greatly appreciate your help.

 

[VaughnH]

A 20L tank is relatively shallow, but you have 96 watts of light on a 20 gallon tank. That is very likely to be much too much, unless you keep all of the nutrients, the CO2, the cleanliness, the water circulation in perfect order. With that much light it is possible the most competitive plants are hogging the CO2, leaving the other plants short of it. How do you maintain good water circulation in the tank, so every leaf in the tank gets water flowing by it? That is necessary with such high light.

 

[hulu]

Thanks for the reply, VaughnH. you are right, I am not sure about the water circulation, the best I could do is placing the inlet and outlet of Eheim 2215 at the diagonal position of the tank.
BTW, do you think temperature could be another reason? I set it to 79F, maybe I should tune it down to 74F? Another thought: I use a airstone 30 min after light off and 30 min before light on, to remove the CO2 (since I could not turn the DIY off). Any concern about this procedure?

A 20L tank is relatively shallow, but you have 96 watts of light on a 20 gallon tank. That is very likely to be much too much, unless you keep all of the nutrients, the CO2, the cleanliness, the water circulation in perfect order. With that much light it is possible the most competitive plants are hogging the CO2, leaving the other plants short of it. How do you maintain good water circulation in the tank, so every leaf in the tank gets water flowing by it? That is necessary with such high light.

 

[VaughnH]

79F is a good temperature, so I doubt that being a problem. Here is some more "evidence": You cut back on fertilizer dosing, and the plants did better. By doing that you resticted the growth rate of the plants, probably by limiting the phosphate available to them. That reduced the demand for CO2 by all of the plants, but it also stopped the CO2 hogs from using it all up, allowing the less competitive plants to get enough to grow, even if slowly. So, I still think you just have way too much light for the amount of CO2 you can reasonably provide to the plants. If you can reduce the light intensity by raising the fixture several inches above the tank, and increase the CO2 bubble rate a little, you should get better growth for all of the plants.

 

[Tom Barr]

I checked my CO2, it has been quite steady for a long time, 2 bubble/sec (sorry, not /min, it was a typo, thanks Vaughn pointing out to me). Plants are pearling like crazy. I had riccia stones everywhere, they start pearling significantly 1 hour after the light is turned on. The problematic plants I mentioned are close to these riccia stones. As Riccia are good CO2 indicater, it seems to me CO2 should not be a problem.

Seems so based on that. As long as you are consistent.

Back 3 months ago, Blyxa has been growing like crazy in the same tank --- at that time I had to sell a lot to my LFS. The only difference is back then , I did not add GH booster, and my CO2 was only 1 bubble/sec. But back then my HC was growing poorly. Things are oppsite now, my HC are spreading green and thick, with contrast Blyxa are almost gone.

Seems the tank is running out nutrients if the CO2 seems fine.
A water change and redose after is all it takes to see. What happens when you do that?

Could this be allelochemicals secreted from one plant inhibit the other, as Diana pointed out in her book "Ecology of the planted aquarium"? Or are there some ferts reaching toxic level in my tank? That would explain when I forgot to add ferts for 4 days, those plants recovered a little bit.

Just wipe the whole allelopathy idea from your mind right now
That ain't it in any case ever.
If you think so, add some activated carbon and see for yourself, that is the control treatment for allelopoathy, something many aquarist have done/do.
Removes all the allelopoathic chemicals asap.
Very easy to rule out any of that.

Lots of folks have riccia, HC and blyxa without issues also.
Something else.

No, ferts are about 10-20 X lower than they need to start causing toxic effects.
Not likely, you'll kill shrimp and fish first anyway. Not dosing for 4 days can cause plants to become limited etc, so that might be it, rather than too much.

Please let me know what your thoughts are. I greatly appreciate your help.

Try a few good water changes, a little patience and allow the tank to get full of plants again, after you remove everything all a sudden, it can take time to readjust, I've done the same thing to some of my own tanks and just needed not to remove so much plant biomass and wait till I get more plant biomass going before some plants do well.

Blyxa was one such plant.
It grows like a weed now, same ferts, CO2, light etc.
How old are your bulbs and what type are they?


Regards,
Tom barr

 

[hulu]

Seems the tank is running out nutrients if the CO2 seems fine.
A water change and redose after is all it takes to see. What happens when you do that?

You hit the point, Tom. Everytime after the water change and redosing, the curled tips seem to become better for a few days. One more confusing thing is that I noticed when the plants, such as Nesaea pedicellata, float to the surface, their leaves grow better there than when they are in the substrate.

How old are your bulbs and what type are they?

The lighting is 2X Current USA Nova Extreme fresh water (2X24 W) T5HO, total
of 96W. The bulbs (2 X 10000K+2 X pink plant grow) are 3 months old.

Thanks alot for the advice, Tom. I bought some rotala recently to increase the biomass. After reading Vaughn's suggestion, I noticed that part of my tank the plants is not moving at all. So I just ordered a Hydor Koralia 1 (400GPH) to increase the circulation.

In summary, the reason could be the following:
1. CO2 not enough for the mentioned plant. (unfortunately can not boost CO2 anymore because it is a DIY setup. But I am going to increase the water circulation)
2. Nutrients deficiency. (again, increse circulation?)
3. Nutrients toxic. (as Tom pointed out, this is low possibility. Plus fish are doing fine.)
3. Substrate problem? (I am using seachem fluorite, maybe replace it with aquasoil?)
4. too much light (96W T5HO) ? (increase the height? I am thinking a way to achieve this)


Thanks again for all the suggestions, please let me know your thoughts.

 

[Tom Barr]

Hulu, please look at the article section under internal DIY CO2 reactor, make one, they cost 2$ to make.

Use it and watch.

Just do this if nothing else.

Regards,
Tom Barr

 

[hulu]

Thanks a lot for all the above suggestions. Here is what I did:

1. Raised the light fixture by 6" to decrease the light intensity and make the tank more evenly lighted.
2. Installed a Hydor koralia circulation pump, now the plants are nicely moving inside the tank.

I will report back the results a few weeks later. Hope this solve the problem. If not, I guess I will have to change the substrate to aqua soil

Hulu, please look at the article section under internal DIY CO2 reactor, make one, they cost 2$ to make.

Use it and watch.

Just do this if nothing else.

Regards,
Tom Barr

Tom, I currently have a external areactor inline with a eheim 2215. Do you mean I need to add another internal reactor?

 

[Tom Barr]

The internal should work better for this tank.
See the design and try that.

Plug the powerhead into the light timer.
That's it.

You likely need more flow through that Ehiem to run the Reactor, you can figure out some way to do that etc, it would be helpful.

It's not so much adding lots of bubbles etc, it's more about even mixing between the diffuser method and the entire tank.

So flow rate of water through it is as important as bubble rate.
More flow= better mixing throughout tank.



Regards,
Tom Barr

 

[hulu]

Thanks a lot, Tom.
I'll start to build one when I got the parts ready.

 

[hulu]

Update:

Co2 could be the reason of the recent plant suffering. I just noticed that my eheim filter had a significantly reduced flow (maybe only 1/3 of its full capacity), so I dessembled everything, the pump head, the canister, and the tubing, and gave them a good clean. Unfotunately at present I cannot run the pump with the inline CO2 reactor, because I managed to break the co2 inject tubing during the cleaning. But the good thing is that the flow is fully recovered!

Due to the increased water circulation and more homogeneous light distribution, I think the plants already show some improvement during last week.

I will update again when my new internal reactor starts to work.

Again, thanks for all the help!