Bba Control And Fertilizers

[Claudio]

Hi,
I have an almost cubic tank, 45cm x 45cm x (H) 48cm, gross volume 90 liters, actual volume more or less 75-80 liters.
I started the tank as a "Walstad method", low light tank in 2015. In 2018-2019 soil started to seems depleted, and I added some fertilizers tabs (Dennerle) to add Cryptocoryne, that restarted to grow again. I was also dosing Seachem Trace, 1 ml every two weeks, and a bit of iron.
Tank was started with garden soil topped with black quartz gravel.

Last summer I rescaped a bit, mainly because a probable lack of nutrients and a very warm period stunted so much the plant growt that I lost some fast plants, like Limnobium and Riccia fluitans.
In October 2019 I added Cryptocoryne crispatula, Marsilea hirsuta, Bucephalandra "Lavandau Green" and "Apple leave", and Lemna minor and a Pothos with roots in the tank as fast growing plants. Few weeks ago I added also a bunch of Bacopa caroliniana.
Other plants that I have are:
Cryptocoryne parva
Cryptocoryne beckettii
Cryptocoryne crispatula
Anubias barteri var. "bonsai"
Anubias barteri var. “pangoline”
Monosolenium tenerum
Vesicularia dubyana ("Java moss")
Microsorum pteropus “narrow”.

Animals are guppy-Endler hybrids, Amano shrimps, and snails.

C. beckettii, C. parva Anubias and Monosolenium I have from an older 30 liters tank (a shrimp tank) from 2012,

I am using a 15W LED lamp that surprisingly allows Marsilea and C. parva to carpet the bottom of the tank, and also the Bucephalandra is growing very well on a stone.

I am using tap water, that is very hard: KH=10, GH=20, but I have grown several species of plants in this water without problems. Cryptocoryne, Anubias, mosses, Egeria densa, Najas guadalupensis, Lemna, Limnobium, Riccia fluitans did very well, provided there are enough nutrients.

Some months ago BBA started spreading, altough slowly, but now are becoming a problem.
Lemna minor and Pothos are growing very slowly, so there is a clear lack of nutrients. I had Limnobium laevigatum for years, but slowly disappeared.

I tested the water, it has NO3 = 0 mg/l and PO4 = 6 mg/l.
I have ordered some root tabs for Cryptocoryne, and I have collected some ferts, but I would like to have and advice about how to dose.

I have:
Seachem Trace
Seachem Iron
KNO3
KH2PO4

I think that I shall not dose KH2PO4 for now, since I already have enough phosphates, and instead I shall start dosing KNO3 and see what will happen. Fishload is really small.
I am not dosing Iron either, since I noticed that if I add 1 ml of it, water start to be "foggy": probably because of hardness and phosphates are precipitating the iron?

Is this a good strategy? How much KNO3 shall I add?

 

[Allwissend]

Yes increasing nitrate will likely help the plant health and thus reduce the spread of BBA. For me BBA spread is alway linked with the need to clean the tank up or plant health being poor. So give the filter a clean, clean as much dirt as possible from the tank.

Target the nitrate levels between 10 and 30 mg/L NO3. So with weekly water changes a dose of 20mg/L per week would likely keep the NO3 levels up.

 

[Claudio]

Yes increasing nitrate will likely help the plant health and thus reduce the spread of BBA. For me BBA spread is alway linked with the need to clean the tank up or plant health being poor. So give the filter a clean, clean as much dirt as possible from the tank.

Target the nitrate levels between 10 and 30 mg/L NO3. So with weekly water changes a dose of 20mg/L per week would likely keep the NO3 levels up.

I already did a good clean-up of some mulm from the botton and a 20% water change.
It is a low-light/no-CO2 tank, so I do not do weekly regular water changes but more monthly or every two-three months depending on the water colour: when the water starts to be too "tinted", I do a water change.
The filter is a simple sponge filter, I clean the sponge when I see that the output start to slow down (again, it happens about once per month).

From the article about low-tech, no-CO2 tanks I undestood that I shall dose a tiny amount of KNO3 weekly (1/4 or 1/8 of teaspoon for my tank, I suppose): is it correct?

 

[Allwissend]

Maybe it can help to increase the frequency of the cleaning routine to help lower the BBA spread, at least for a while to see if you get a slowdown.

Yes for low tech tanks the growth is not likely to use up a lot of NO3 so there is no need to dose as much. That being said, if your light is suitably low, a bit extra NO3 does not hurt. Also since you have 0 now, it can be that plants take up more NO3 at the start. After they replentish their supplies this uptake will slow down.

 

[Claudio]

Thank you, I planned to clean a bit more and remove a bit of vegetal debris. I will start dosing a bit more NO3 and see what happens.