My problem: I have a 29 gallon tank that has been set up for about 4 years. At the present time the left half contains about 40 C. wendtii plants, all healthy and sending out runners. They are descendants of a few that were planted when the tank was set up.

I can't get anything to grow on the right half. Most recently I planted 8 healthy Vallisneria spiralis (?). They were raised in another tank, had strong white roots, and were sending out runners. After 6 weeks it became apparent that they were dying. They had produced no new leaves and the roots were dark and not growing.

At the same time I also planted 6 healthy E. tenellus, also from another tank. These remained green but got smaller and smaller and have almost disappeared.

Two anubuias, which had been in that tank for about 2 years, have remained healthy but show no growth.

Three days ago I added several short stems of Hygrofila polysperma. They already show signs of decline.

The aquarium is lit by a new Coralife 65 watt CF fixture. CO2 in not injected, but there is a soil substrate.

That soil substrate is 4 years old and should have long been depleted of many of its nutrients. However, Walstad maintains that the droppings of the fish will make up for that loss. Since the crypts, heavy root feeders, are doing well, I assume that the substrate is not the problem.

Nitrate (20 to 30 ppm) and phosphate (1.5 ppm) are within normal limits. GH is 22 degrees, some of which is from Equilibrium. Flourish is added monthly.

I have several other soil-based tanks that are maintained in a similar (but not identical) manner. All have a profuse growth of a number of plant species. Some contain C. wenditii, but not in the density of the problem tank.

The only thing that I can think of that would be preventing the new plants from growing is that the large number of crypts is somehow inhibiting the growth of newer plants.

Can anyone suggest another possibility?

Thanks,

Bill

(BTW, I Google'd 'cryptocoryne allelopathy' and found a few sites but nothing conclusive.)

In my limited experience, it seems to me that crypts (at least the wendtii type) are very forgiving. The other plants you are trying are not as much so. You would know best what the difference is between this tank and the ones you are getting the other plants from.

Hi Bill,

Have you had a chance to gravel vac that section? If compacted heavily, it can produce hydrogen sulfide which is toxic to all.......

IME I had 1/2 of my 180 with wendti at one point and did not cause any issues. Was doing a bit of c02 at the time, regular floro tubes, but no other ferts using flourite. Was able to grow other things with no problems.

Clean out that side of the tank and ensure all old roots, etc is gone.

Then again try some of your new cuttings.

I don't think the wendti is inhibiting it.

I think the specific area is the problem.

Let us know.

What happens to a house plant when it becomes root bound?

4 years is a long time, try pruning it.
Add some "Mud cubes", that will address nutrients pretty well.

In general, I've found when Diana and others make the claims about some plants waning and ebbing, it's always due to a lack of some nutrient.

However, it also might be due to too much organic matter that's built up over time in the sediment.

The sediment is so reductive, that the other plants cannot establish their roots whereas the Crypt has a massive O2 pipe/root system and are not as effected.

I'd go in a cut some out.
Add some new mud cubes.

If you want to test allelopathy, add some activated carbon in the area and add a lot and mix well into the sediment.

This will mop up any allelopathic compounds fast.
Add AC to the filter if you think the allelopathics are in the water column.

Fairly simple test.

I think most of the speculation many claim with Allelopathy are merely differences in the nutrient tolerance between plant species, not allelopathy itself.

In other words, I've never seen a case yet that was due to plant- plant allelopathy in aquariums.

Also, at higher levels of nutrients, CO2, light, with the respective faster growth rates(10-20X), we should also see similar increases in allelopathic chemicals and even if not that much, at the bare minimum, at least the same as the non CO2 situation.

I've not seen any evidence growing this plant in non CO2, CO2 or emergent situations yet.

Regards,
Tom Barr

Is it possible that the crypts are using up the nutrients in the water, but having a big root system, can continue to grow from root feeding? That would leave the newly planted vals and microswords short of nutrients, but without the roots needed to feed that way.

Also, I have always had problems getting vals to start growing when first planted. They almost always shed all of their leaves, leaving only a rooted stub. Eventually that stub sends out new leaves and the vals become the nuisance they can become. Since I have never had E. tennellus grow for me I can't comment on that.

Thanks for your responses!

I will assume that the substrate is the problem. I'll replace it in the half of the tank in which things won't grow and plant new plants.

Should I expect the substrate that I remove to be crowded with crypt roots? If it isn't, what will that mean?

There are plenty of nutrients in the water column, excepting carbon. If plants are able to make use of ferts in the water column, why won't the plants simply use the substrate to hold on to, and get their food from the water? The H. polysperma which I added a week ago should be able to do that if any plant can, yet they started dying on day 2 and are just about dead now.

I'll post the results of this in a few days.

Thanks again.

Bill

My understanding is that higher tech tanks generally get more water changes than lower tech tanks. Which means that the level of allopathens, along with everything else, will be reduced.

Could that not explain allelopathy not being seen in high tech tanks?

Would a plant growing more slowly produce more or less allelopathen per unit of growth than a plant growing fast? Maybe there is a difference there, too.

Would a plant growing faster be able to cope with more allelopathens in its environment than a plant growing more slowly?

Bill,
I don't really think this is a good assumption. Instead of looking at allelopathy, which as far as I can see is akin to witchcraft, it would be more productive to troubleshoot the macronutrient content of the tank.

You mentioned that the 30 gallon tank is illuminated by 65 watts of Compact Fluorescent. If so this is just over 2WPG and really no longer qualifies as a low tech tank. Further, you noted that no CO2 is being injected. So a fast growing stem is placed in a high light environment without CO2 supplementation and it fails. I would conclude that the failure is at least in some part due to the inability of the stem to adapt to the low CO2 levels while being driven to high CO2 uptake via light energy input.

I think that every hobbyist has a tank wherein some plants do well and other plants struggle or fail completely. Some plants are more adaptable by having more efficient nutrient uptake and processing mechanisms. This adaptability enables them to succeed in a wider variety of environmental conditions, including more stressful environments than those with less efficient systems.

The crypts may have adapted to the tank conditions and have had 4 years to do so whereas a new plant may have difficulty under these conditions.

If you wanted to test the possibility of CO2 starvation you could add CO2 either by gas injection or by the addition of copious amounts of Excel. If you wanted to test the possibility of light driven starvation then you could insert say, a 30 watt bulb or otherwise screen the 65 watt bulb to reduce the amount of light entering the tank. A combination of these actions would probably work.

Additionally, it's unclear how you are determining the nitrate and phosphate levels. Are you measuring with test kits, or is that from your water report, or are you adding this amount weekly?

There is enough ambiguity to question the dynamics of nutrient/CO2 uptake within this tank configuration. Only when these conditions are verified, and when you are satisfied that the conditions for proper growth exist within the tank can we then move on to other possibilities regarding unknown assailants/agents.

What we do know for certain though is that rapid degeneration of plant tissue is a classic symptom of CO2 starvation often exacerbated by poor nutrition.

Hope this helps.

Cheers,

No, the observations:

We can also not do water changes in high tech high growth tanks.
The production of secondary compounds generally matches the rates of growth as well(not all, but in general). again, we do not see presumed or suspected allelopathic effects.

As mentioned, the control is adding activated carbon(AC) in the filter for the water column effects and AC in the sediment for root based effects. So adding AC should remove those effects.

Likewise, the same can be done in a non CO2 system.
Standard protocol is using something that will rapidly absorb the chemical and AC is an excellent choice.

BTW, there's have never been a single study(See Ole's refute in Articles here or on Tropica's web site) showing a significant effect in any natural system. I'm not saying there is not any, it's just never been seen or found to be significant and it's not from a lack of trying to find it.

I've refuted it with some rather simple test that any aquarist can do and see for themselves if they can see any differences over time. No one has yet. Self competition for resources is also a possible factor not considered by many folks as well. And then just basic good horticulture, eg trimming the and thinning plants, making sure there are enough nutrients/CO2, decent lighting.
Those are by and far the largest issues and where folks see the most impact.

Also, how does the plant know how big the water it lives in is?
What about rivers and streams that are unidirectional? What good would that be for the water column? Swords, Crypts etc are all very much stream and river plants.

They need large roots for mechanical reasons as well as when the water recedes and they no longer can get water for the leaves any longer.

If you want to read more, it's a long review:

SpringerLink - Journal Article


Regards,
Tom Barr

Some plants grow very well only when there's plenty of nutrients and CO2 etc and then they grow like mad, others will trade off high rates of growth for slow and steady growth over a wider range of environmental parameters. So which plant would you predict would do best under lower levels of CO2 or nutrients?
I think given some time, the stem plant will adapt, but placing it in a very competitive area with another plant that's well established is not a good test.
You do not really see that in natural systems except with nasty competitive weeds like Hydrilla etc. That plant does not produce allelopathic chemicals, it beats on other plants by physiological means(excellent nutrient uptake, CO2 uptake and C4 like MET, Root and water column uptake, very low light compensation points) and ecological(very long lived Tubers + turion formation, fragmentation, very dense light blocking canopy, extremely dense biomass, rapid rates of growth).

These traits are worth more in terms of competitiveness than allelopathy and far more effective in any aquatic system. Light is the main competition in aquatic systems for both plants and algae.


Regards,
Tom Barr