Plants turning black - Help!!

[Robmana]

Hi All,

Need some help please.

My plants appear to be turning black pretty quickly and I’m trying to understand what I can do to help them. I add liquid Co2 to the tank daily, do regular water changes and add fertiliser, and still they’re turning black. See photos attached.

Any advice would be great

Thanks
Rob

 

[Byron]

The "black" is not the plants themselves but algae. Tbhis is caused by an imbalance of light/nutrients. The light may be on too long, or too intense, or the nutrients may not be sufficient to provide enough for the plants.

Do not use liquid CO2, it is not needed, it can be harmful to fish as well as plants, and even bacteria.

Data on the light, plus any other fertilizer/plant additives?

 

[Oblio]

I'm also new to plants and have the same issue. In my case it is algae.
What lights are you using, how long are they on, what level? (if adjustable). Are you using root tabs or liquid fert? Type and rate?
The plant SMEs here will give good advice base on your answers and possibly more.

 

[Robmana]

The "black" is not the plants themselves but algae. Tbhis is caused by an imbalance of light/nutrients. The light may be on too long, or too intense, or the nutrients may not be sufficient to provide enough for the plants.

Do not use liquid CO2, it is not needed, it can be harmful to fish as well as plants, and even bacteria.

Data on the light, plus any other fertilizer/plant additives?

Brilliant advice on the Co2, thanks.

I attach a photo of the fertiliser I’m using and on the light, I have it on from 8am through to 4pm, to emulate the winter days. I have just reduced that down by an hour each side to see if that make a difference.

In terms of intensity, I have the daylight hours set at green and blue 100%, red at 70% and white at 90%

 

[Robmana]

With attachment

 

[Robmana]

Should also say that I have added ‘API Prevent Algae’ in the past but worried that the snails and shrimp will need to get their nutrients from elsewhere if I clean the tank of all algae?

 

[Colin_T]

Does the black coloured algae wipe off in a film?
If yes, then it's blue green algae.

A few of the plants in the tank are not true aquatic plants (Anubius) and grow very slowly when kept under water. If you add fertiliser and lots of light to a tank with slow growing plants, they don't use most of the nutrients or light and algae will grow instead.

Cut back on the fertiliser.

Reduce lighting times by an hour a day and monitor it over the next few weeks.

Reduce the dry food going into the tank

 

[Oblio]

Should also say that I have added ‘API Prevent Algae’ in the past but worried that the snails and shrimp will need to get their nutrients from elsewhere if I clean the tank of all algae?

I believe the (wise) consensus is to treat the cause and to use chemicals only as a last resort.

 

[Robmana]

Does the black coloured algae wipe off in a film?
If yes, then it's blue green algae.

A few of the plants in the tank are not true aquatic plants (Anubius) and grow very slowly when kept under water. If you add fertiliser and lots of light to a tank with slow growing plants, they don't use most of the nutrients or light and algae will grow instead.

Cut back on the fertiliser.

Reduce lighting times by an hour a day and monitor it over the next few weeks.

Reduce the dry food going into the tank

The black algae seems to have infected the leaves rather than be sitting on top, so no, can’t clean it off. I will take your advice and monitor over the next few weeks.

Many thanks

 

[Oblio]

In terms of intensity, I have the daylight hours set at green and blue 100%, red at 70% and white at 90%

In my case, I've dialed RGB and W to 80% (from 100%) and reduced time from 8 to 6 hrs a day. This seems to be helping so far. I've also added Pothos to the tank to help keep nitrates down between water changes.

 

[Robmana]

In my case, I've dialed RGB and W to 80% (from 100%) and reduced time from 8 to 6 hrs a day. This seems to be helping so far. I've also added Pothos to the tank to help keep nitrates down between water changes.

Ok, applied the same to lighting, will be interesting if these changes work. Thanks again

 

[raylove]

It can be hard to work out what you are lacking or what you have an excess of because we can't test for every nutrient.
I have had similar issues to yours which I eventually put down to high nitrate, something you can easily test for. I find that many plants grow poorly if nitrate is above 30ppm. It's a catch 22 situation because once they get going they will probably keep nitrate low. If like me your source water is already at 35ppm you'll probably have to do what I do - I use a nitrate removal resin to get the level down to 10ppm then I take it out and let the plants grow! Nitrate in my planted tank now stays at zero - floating plants also help to soak up nitrate.
Because I don't want to add nitrate I use a nitrate free fert, however, these also tend to be phosphate free. Phosphate test kits are available so I do test for that too and I end up having to add phosphate otherwise my level goes to zero and I get issues.
PS phosphate ferts are expensive so go to YouTube and find a recipe to make your own!

 

[Oblio]

Ok, applied the same to lighting, will be interesting if these changes work. Thanks again

Caveat/Full disclosure: I'm fairly new to this, so if someone here with experience tells you differently, listen to them

 

[Colin_T]

Ok, applied the same to lighting, will be interesting if these changes work. Thanks again

You don't want to reduce the lighting too much. Just reduce the time or the intensity for a couple of weeks and see if there is an improvement. Don't reduce both time and intensity, just do one or the other. And only reduce the time by 1 hour.

Plants need at least 8 hours of light per day.

 

[Robmana]

It can be hard to work out what you are lacking or what you have an excess of because we can't test for every nutrient.
I have had similar issues to yours which I eventually put down to high nitrate, something you can easily test for. I find that many plants grow poorly if nitrate is above 30ppm. It's a catch 22 situation because once they get going they will probably keep nitrate low. If like me your source water is already at 35ppm you'll probably have to do what I do - I use a nitrate removal resin to get the level down to 10ppm then I take it out and let the plants grow! Nitrate in my planted tank now stays at zero - floating plants also help to soak up nitrate.
Because I don't want to add nitrate I use a nitrate free fert, however, these also tend to be phosphate free. Phosphate test kits are available so I do test for that too and I end up having to add phosphate otherwise my level goes to zero and I get issues.
PS phosphate ferts are expensive so go to YouTube and find a recipe to make your own!

Thanks Ray.

I actually use RO water (found an amazing low cost provider) and add Replenish to bring minerals back the right level so my nitrates are negligible. I also added some floating plants this afternoon (can’t remember the name!).

Let’s see how things go with reduced light over the next few weeks!!

Thanks again!