Algae affecting bottom plants... any ideas?

[Mr.Manjushri]

Hi folks,

Subject is a new tank (3 weeks old), with the following specs:
- 80cm, approx 140L
- Eheim 2178 (professional 3e 600T) with 2L Mechpro, 4L Biomech and 2L Substrat pro
- 4x 24W T5, now at 12 hrs/day
- Pressuried CO2, approx 1bubble/sec, using Dennerle CO2 'ladder'
- Dosing Dennerle E15 FerActiv (1 tab) and V30 Complete (3ml) alternately every week.
Note: Plants are sitting on 5L of nutrient substrate under gravel
- Weekly 40-50% water change
- Stock: 20 'amano' shrimp, 12 Hyphessobrycon Columbianus

Most plants growing well, but Hemianthus Callitrichoides and other low/bottom dwellers struggling, and are now being covered with a thin brown algae.

Have noticed they are no longer producing much-loved telltale bubbles of O2 (they were the first couple of weeks). Thinking more CO2 (thought I'd ask here first before I put the fish in jeopardy) or less light, although the later seems counter-intuitive since the plants which are closer to the light source seem to be doing better...



Any comments, advice or tips much appreciated.

 

[ceg4048]

Hello,
Plants that are closer to the light might also have better access to CO2 than plants at the bottom of the tank. Gasses rise, they do not sink. You have too much light for much too long of a photoperiod.

I would remove at least half of the media material in the filter to get more flow and I would increase the injection rate. It won't be long before the plants that are doing well now start to do poorly.

Cheers,

 

[Mr.Manjushri]

Good suggestions, thanks ceg.

I will reduce the photoperiod to 8hrs. Would it also be wise to cut the lighting by half except for a 'midday' burst of 2-4 hrs? I was under the impression 2 wpg was a good target for lighting (admittedly I have approx. 2.5 wpg) but maybe I misunderstood something among the masses of information I've been trying to absorb over the past month!

Small incremental increases in the injection rate are also on the agenda for the next week. I wonder if it would be worth investing in an inline diffuser... or is that bubble ladder effective enough?

I can really do away with half the media in my filter?! Then I assume it will be the first mechanical half that gets lynched, right? 2L biomech and 2L substrat pro should do the trick then.

Thanks again

 

[ceg4048]

Yes, flow is much more important than media total. You should cut the light by half and forget about burst for now. 2wpg is good if it works, but it's not working at this time because of all the other things that are problematic. Plants do not care about wpg. Only the people selling light fixtures care about wpg. It is definitely worthwhile investing in an inline device. When you have a better flow/distribution and gas diffusion technique you can increase the light, but right now light causes stress.

Cheers,

 

[Yo-han]

Agree with ceg4048. 2wpg (of thats means anything at all) might work if everything is in balance, but I don't think you can pull that off without macros. V30 may sound complete, but it doesn't contain nitrate or phosphate. The dropchecker seems quite dark green for that amount of light as well. So either decrease the amount of light (this way the demand for NO3, PO4, CO2 etc is lower) or increase CO2, PO4, NO3 etc... Good luck!

 

[Mr.Manjushri]

Will follow your advice and keep you posted on results in a couple of weeks.
Many thanks

 

[Kannu]

I would also try and introduce a short break of 30-45mins between the 8hrs photoperiod as that should discourage the algae. Also is there a way you can increase the flow towards the bottom of the tank?

The layout looks good BTW.

 

[foxfish]

Why would you stop the lighting at mid period! That was a popular thing to do back in the 80s & there was a guy on the forum who tried that method a few years back but I don't think it really makes any difference ?

 

[Henry]

Definitely flow and CO2. I have changed to an inline diffusion method and improved flow, and have seen an almost immediate improvement in plant growth. My fast growers reacted to the changes almost overnight, and plants near the substrate have shaken the diatoms that once lurked.

I was skeptical at first, but Clive speaks the truth!

 

[Kannu]

Why would you stop the lighting at mid period! That was a popular thing to do back in the 80s & there was a guy on the forum who tried that method a few years back but I don't think it really makes any difference ?

I dont believe there is conclusive proof that a broken photoperiod does or does not benefit algal growth. It seems to work for me and I continue to maintain a short break in my tank.

In this case, since the plants have stopped putting out O2 bubbles, it suggests that the CO2 output may be less, then the break in photo period will allow enough CO2 to build back into the system when the lights come back on.