Black/brown dust on older growth, help please.

[Sergey]

Hi guys,

I've noticed some black or brown algae has been building up on older leaves of my Anubias and some similar stuff is slowly creeping up Riccardia carpets, so I'd like to ask for help identifying and fixing that mess.

Tank description is as follows:
- 20L Aquael nano cube tank, appprox. 3 months old;
- Light is medium (visually), Chihiros A25 at 70%, many floating plants (Salvinia), photoperiod 5-4-5 (4 hr siesta in the middle of the day);
- Filtration: internal Dennerle filter corner filter;
- Pressurised CO2, drop-checker is stable light-green; pH drop around 1-1.2 (from 7.8 to 6.6), with water kH 3-4. I don't switch off CO2 at night.
- Ferts: Tropica AquaSoil substrate + EI dosing;
- Plants: mostly slow-growing (Buces, Crypts, Anubias); Riccardia moss; quite a lot of floating plants (hornwort, Salvinia, a bit of duckweed).
- Livestock: around 15 cherry shrimps, some snails and 1 sparkling gourami.

The tank had been neglected for about a month until 3 weeks ago, as I was on vacation and no-one was handling it, but last 3 weeks I've been following dosing/water changes quite rigorously. However, it didn't make things better; the positive change I noticed is that plants started to grow faster; I assume it's because of better dosing and increased light.

Any advice will be greatly appreciated.

 

[Kalum]

Better growth will end up meaning better algae control as the plants will out compete it

That's quite a lot of light for a tank of slow growers so you could try and reduce the light intensity and duration (siesta doesn't benefit anything in my opinion but it's up to you if theres a reason behind it for viewing etc..) but my main thing would be to rub/clean all leaves and algae that you can and go a couple of weeks with water changes every 3/4 days, keeping things as clean as possible gives the plants the best growing conditions which will help with algae

 

[Sergey]

Why do you think it's a lot of light? I'm asking because I still struggle to figure how much is low and how much is too strong. Visually, this tank is probably the dimmest one I've ever had.

Interestingly, at first I also thought that running this lamp at 70% would be overkill. Previously I ran low tech/no co2 setup in this tank, and 40% was just enough. However, with the new scape with the light lower than 60% plants would stunt, the first batch of staurogyne simply melted within a couple weeks. I think it's because of a) driftwood gives a bit of shade; b) tannins from said drifwood (water is visibly yellow), and c) floaters cover almost 50% of the surface. Actually, I thought my algae problems were caused by too little light.

I'm going to do more frequent water changes, I'll try twice a week around 50%. How should I change the fert dosing? Should I dose after a water change to account for removed amounts?

 

[Dolly Sprint 16v]

Algae is caused by not get the balance between the following: fertz / lights / Co2. Your tank has slow growth plants so you dont need masses of light, 5 hrs would be fine and one lighting period - splitting the period 5.4.5 does not help. Plants consume fertz during lighting period so they absorb the fertz in the first lighting period, then the lights go off and the plants will think it night time, then the lights come on again and absorb the remaining fertz or no fertz left as they were consumed during the first lighting period.

No issue doing two water changes but stop and revert back to one when the algae starts to disappear, as you are using E.I 50% change once a week and dose after your water change.

Co2 injection must be very low if you never switch it off (running 24hrs) you could up you injection rate (more Bps) switch co2 on two hours before lights come on (light green drop checker required) and switches off when the light go out.