Plant newbie with 6 months limited growth

[froggytank]

Hi all, what a lovely forum. All my information is below. I don't have a green thumb and I was wondering about how best to promote growth in my tank with minimal intervention. For the first 6 months, everything grew like gangbusters, with the java fern breaking the surface, the Amazon sword 8 inches wide, and the duckweed multiplying in scoops. Then over 3 months the Amazon sword got wispy and died, the java fern reduced to half height, and the duckweed stagnated and turned lighter. This has stayed stable for another 3 months. In general I'd prefer to keep costs and interventions to a minimum and not give risk to the animal inhabitants as well. Here are my questions in no particular order:

A) What is your diagnosis for the stagnating growth and what can be done about it sustainably?
B) Are the black spots on my Java fern cause for concern? (picture attached)
C) What plants could I acquire that might thrive in my environment and substrate?

The tank:
1. Size of tank: 35L Dennerle Nano Tank 40cmx32x28; heater set to 76 degrees F
2. Age of the system approximately: 1 year
3. Tap water parameters: I don't have a testing kit; water company claims 7.4pH and hardness of 4gpg
4. Filtration and Media: Dennerle Corner Filter 40L (Corner Filter - Dennerle (EN)) no additional media besides included floss and sponge
5. Lighting and duration: ~10 hours/day Dennerle Trocal LED (Trocal Power LED 5.0 - Dennerle (EN))
6. Substrate: Dennerle Borneo Brown nano gravel (which I was sure was sand until looking it up now) Dennerle Nano Shrimp Gravel - Borneo Brown-2kg
7. Co2 dosing or Non-dosing: nothing
8. Drop Checker: none
9. Fertilizers used + Ratios: none
10. Water change regime and composition: weekly ~40% with a siphon and Seachem Prime in the tap water
11. Plant list + Invitro/Emersed: java fern, pothos, duckweed, grass I can't recall, unknown arugala-like stowaway
12. Inhabitants: 3 African clawed frogs, guppy, platy, pleco
13. Full tank shot and surface image

 

[hypnogogia]

9. Fertilizers used + Ratios: none

That’s your problem. You need to feed your plants if you want them to grow, so you might want to start using an NPK fertiliser. I think in the US NilocG is a good one.

 

[froggytank]

That’s your problem. You need to feed your plants if you want them to grow, so you might want to start using an NPK fertiliser. I think in the US NilocG is a good one.

Thanks for your reply. The inhabitants don't provide enough for the plants? And a fertilizer such as that, won't it possibly cause a nitrate spike?

 

[John Troy]

Although I cant be certain, I don't think fish waste provides many micronutrients, mainly just nitrates, so it may be useful to add a micronutrient fertiliser. Given you don't have much plant mass I think it would be unwise to add more nitrates, especially since your highly stocked already. Obviously CO2 injection practically always helps plant growth. In terms of plants that would do well, given you dont have tons of algae despite low plant mass and high stocking it means your tank probably doesnt have an excess of nutrients and your light probably isnt very strong, also your substrate isnt particualy nutrient rich, so the best plants to go with would probably be something like anubis or bucephalandra which are easy to grow and you could attach to the rocks/wood in the centre. Anarchis elodea is always a good options since it grows rapidly in practically all conditions and also oxygenates your water, also it can be floating or rooted, either way it obtains nutrients through the water column. Although it may outcompete your slow growers in low nutrient conditions.

Thanks for your reply. The inhabitants don't provide enough for the plants? And a fertilizer such as that, won't it possibly cause a nitrate spike nutrients necessary for plant growth, mainly just nitrates.

 

[hypnogogia]

Fish add some, but not sufficient, otherwise your plants would be thriving. As to nitrate spike, your plants will use the nitrates, so I wouldn’t worry about it.

Also, it’s not lack of CO2 as your floating plants (which are not CO2 limited) are also not growing. They look pale and under nourished.

 

[MarcusA]

Fish food provides nitrogen, phosphorous, and many micronutrients. It’s not so good at providing potassium (K) and iron (in a usable form). Most here contend that N and P fertilizer are harmless even at high doses and that nitrates are only a concern in that they act as an indicator of organic waste in unfertilized tanks. Nonetheless, if you are looking to minimize your fertilizer intervention, try adding just potassium sulfate and ferrous iron. You can use seachems potassium and iron products if you want an off the shelf solution.

 

[Bradders]

I would also say that plants grow. More growth, more demand on food. It is possible there was enough ‘food’ (although nutrient deficient) at the start but now the fish waste can no longer support the plants size and demands.

 

[keef321]

Agree with others here, it is likely due to lack of fertiliser. We know the duckweed is getting access to co2, 10 hrs of light, but stagnating, therefore this points to a lack of food = fertiliser. We wont know exactly which food they are missing, so use a good all in one.

 

[dw1305]

Hi all,
What @keef321 says. I'll add in his tank pictures, as they may be of interest - <"Cloudy Water Hazy Water and Algae!">.

And a fertilizer such as that, won't it possibly cause a nitrate spike?

Again what the others have said. Nitrate (NO3-) levels will rise, but NO3 isn't actually toxic to fish until you get to <"very elevated levels"> & <"Nitrates">.

It is only really planted tank keepers who add nitrate (via a compound like potassium nitrate (KNO3)) and we do this because nitrate levels fall in our tanks as it is taken up by plants. In other cases the high levels of nitrate are the "smoking gun" of the microbial oxidation of ammonia (NH3) and nitrite (NO2-) and these compounds are toxic.

cheers Darrel

 

[froggytank]

Thanks all for the advice. I will try a small amount of NPK liquid fertilizer from my store (unless you believe root tabs or salts or something are better).

Do you think it is important to add iron at this stage or I can wait on that?

A solid layer of waste accumulates each week under rocks and wood each week (probably because of the frogs). Is it helpful to vacuum-siphon the substrate or should I essentially never do that despite the occasional messiness? Should I disturb the substrate at all when mulm is accumulating on the sides (see picture) or do I have to let it be?

 

[hypnogogia]

I'd suggest using an all in one fertiliser that contains NPK and micronutrients (including iron). I’d also keep the substrate clean by syphoning off the mulm but being careful not to disturb the substrate.

 

[froggytank]

I added a couple drops of NilocG Thrive-C all-in-one fertilizer to the tank on Tuesday, about a quarter of a dose or less. Limited effect on the plants so far. This morning I found one of my frogs bloated and unresponsive, likely passed away. Unfortunately the fertilizer experiment may be at an end, since I can't help but connect the two events

 

[hypnogogia]

Sorry to hear about your frog. A 1/4 dose is unlikely to make a difference to the plants. And I’d surmise that the death of your frog is unrelated to the fertiliser.

 

[MarcusA]

Sad news about your frog. I’m sorry to hear it. Nilocg is a generally well regarded brand. I use their dry fertilizer on my tank. Like hypnogogia, I really can’t imagine that a quarter dose would harm your frog in any way. When I fertilize, my guppies will bite into the pure aquarium salts before spitting them out, and no harm comes to them. If you are afraid to fertilize, I’m not sure what options that leaves you in regards to saving your plants.

 

[froggytank]

My understanding is that frogs are more sensitive to chemical changes than fish on account of their permeable skin

 

[dw1305]

Hi all,
I'm really sorry for your loss.

My understanding is that frogs are more sensitive to chemical changes

There is definitely evidence that high levels of chemical pollution (including nitrate (NO3-)) have lethal (and sub-lethal) effects on amphibians <"Croaking Science: Amphibians and Chemical Pollution">.

more sensitive to chemical changes than fish on account of their permeable skin

I'm not sure there will be much difference. Not all fish have scales but ~all fish have gills, and these are highly permeable surfaces where ammonia (NH3) and dissolved gases are exchanged.

If you are afraid to fertilize, I’m not sure what options that leaves you in regards to saving your plants.

Honestly healthy plant growth is the best, and most effective, way to maintain water quality. Plants remove <"all forms of fixed nitrogen"> and are massively <"net oxygen producers">.

cheers Darrel

 

[ValleyMykel]

The java fern having some dark coloration on some of its leaves is pretty normal with its older leaves. If you start seeing small dots, they are baby ferns. I personally plant new java ferns I buy that have these dots along the leaves, which results in an
explosion of baby ferns.

Somethings that stand out to me for your concerns are that may seem a bit obvious is the pothos being partially submerged, which it shouldn't be, the 40% dilution per week of your aquarium water with tap water of unknown concentrations (most likely within or on the clearer side of drinking water standards), the lack of any organic litter in the form of detritus or dead tree leaves, the lack of any snail colonies, and the overall cleanliness of the tank itself. Its definitely lacking nutrients, and I would like to try and provide a solution that won't require spending money as I also do some sand/inert substrate plant growing and spend no money on fertilizers and manufactured soils.

Add some dead, brown (not green or yellow) tree leaves from outside. Add pest snails that you can get for free at any pet store that doesn't like em. (preferably small trumpet snails). Lessen the frequency of your waterchanges and cleaning (if any), and do a quick check of your NO3 levels to see if there any. You may be diluting them too quickly every week.

The dead tree leaves (and a lot of fish foods) contain most, if not all, of the micro/macro nutrients that you need for plants. The only thing that is needed is for animals, mostly snails and other fauna, to break them down and recycle it back into your substrate through bioturbation as well as dissolve in your water column. You should start seeing a small layer of detritus begin to form overtime on top of the sand, which will eventually become mixed with the sand and create a natural soil that has the capability to support large plant root structures. I have observed this process over the span of a few months, and its insane how healthy it can become. You can give it a little head start by boiling the leaves first, or cutting them up into fine strips.

Ideally, I go for dead tree leaves that I sample from ponds, since those tend to be already quite soft and established to sink, and often have extra cultures of fauna that I'm looking for.

 

[froggytank]

@ValleyMykel The frogs like hanging out in the pothos and it hasn't had any problems so unless there's a toxicity concern, I think it's ok for it to be partially submerged. I'll look into the brown leaves. The dots on the java fern are actually small black holes which online resources indicate is a mineral deficiency

 

[ValleyMykel]

The dots on the java fern are actually small black holes which online resources indicate is a mineral deficiency

Yeah, generally pin holes on most plants are a deficiency with manganese, but I have heard some statements that suggest java ferns are potassium hogs and exhibit similar symptoms in presence of low potassium. Which, someone can correct me on of course. I do spot a few outer leaves that look much healthier and newer, in my eyes usually means that the older leaves are just being phased out especially if they were the original leaves before they were put in the aquarium. Only one way to truly find out is to just test the concentration of those nutrients in your water, which can get a little pricey. Personally, I trim off the older leaves that are showing these symptoms, and if the plant as a whole still shows these problems, then I determine what the deficiency is and try to address a fix from there.

it hasn't had any problems so unless there's a toxicity concern

I've always had pothos leaves above water, so I can't say for certain that it will cause toxicity if submerged and I haven't seen many people report such a problem. Only thing close is that, after a while, the submerged leaves eventually start dying. So as long as nothing goes wrong, I take back what I said and you should be fine with it partially submerged.

Alternatively, if you like that pothos look, there are some varigated anubias varieties you can try, like Anubias "jade" and "panda marble", that look pretty similar to pothos and are fully aquatic.