[Esahc]

My tank is a 20gal long, dirted and planted with no co2, overfiltered and understocked according to Aqadvisor, and gets ~50% weekly water changes, and I just can't quite seem to shake the green dust algae and cyanobacteria. I've tried reducing the light cycle, but my first floor is 90% window, and pretty much any part of the house gets 10-12 hours of strong indirect light on at least one side of the tank. I've managed to defeat the worst of the dust algae with diligent scraping and a pair of amano shrimp and leaving my snail infestation to flourish, but the tank looks pretty terrible and ratty. The pond snails are destroying my plants instead of eating the algae on them, and I'm about at my wits end.

Is there anything I can do to control the algae without reducing the photoperiod? even if I cut the light early, the sunlight through the windows is bright enough we can't tell the difference between having the light in the tank on or off.
Would a CO2 system help? I've been avoiding them because they're either expensive or messy, but I'd be willing to screw around with a diy yeast contraption if it'll help the plants crowd out the alae
Would a larger volume of water help? since it's a 20 long, and I have two 20gal filters running(the heater is also too large and would work on a larger tank), I think I could conceivably get a 30 gal tank and still use most of the same equipment, if the larger water volume would mean easier to control algae.

 

[corina savin]

A larger water volume will not help with algae. I had 4 different kinds of algae in my new 180G and I don't have to tell you what is like to scrape 180G tank. That was more than a year ago. I added pressurized CO2 without much success. Turned out- I was over-fertilizing the water column; the substrate (Aquasoil mixed with Fluval) was seeping enough nutrients into the water. Eventually everything balanced, plants were growing, did not have to scrape algae for more than 6 months. Until last month, when my light fixture broke, half of the bulbs are not working. While waiting for the "parts", plants stopped growing, old leaves turned brown, algae are taking over again. So, IMO less light does not mean less algae. Unhappy plants will encourage the growth of algae.

 

[Esahc]

I guess the trouble is figuring out what's making the plants unhappy.
The tank I'm having trouble with gets no fertilizers other than the waste the fish produce and the excess food that the snails or shrimp don't eat, and no co2 at all.
My tank seems to have gone in the opposite direction of yours; everything was fine when it was first set up, plants were healthy, and the snails weren't overcrowding, Algae started showing up about six months after setup, took over within a few weeks and has stayed a problem through two blackouts and a complete teardown where I replaced all of the substrate (peatmoss mixed with ecocomplete with a sand cap to topsoil mixed with peagravel with a 'sand' [coarse sand or fine gravel] cap) and scrubbed the driftwood and plants as free of algae and possible.

The snail population has exploded to the point where I'm now netting and pulling out 15-20 a day for the last week with no visible dent in their numbers, and they're chewing my swords to lace, which I'm sure isn't helping at all.

Maybe with a taller tank I could fit more stem plants to absorb nutrients from the water column faster? the tank is predominantly amazon swords with one little wenditii and a smallish clump of hornwort. I have no floating plants, because of course everything useful is illegal to own, trade, or transport here, so I guess that could be the problem. (Texas is kinda strict about invasive species.) Adding more plants to the current tank will just make everything overcrowded, unless I completely remove the swords(they've gotten HUGE, but ragged and unhealthy at the same time.) and replace with stems?

At this point I'm open to basically anything that will get rid of this algae.

 

[Als49]

Try adding some floating plants.

They're fast growing and helps absorbing excess nitrate from water column, and they also help giving some shades since too much nitrate and light are usually the cause of green algae water.

And also do 30% WC every other day. That should helps.

 

[Esahc]

we must have posted nearly at the same time. Unfortunately I live in Texas, and 99% of floating plants are completely illegal here, otherwise I would absolutely love to get my hands on some.

the 30% w/c every other day might be more doable, but it's going to be a stretch, and I'd really rather not have to rely on that with the semester coming up. I'm a student, and things get incredibly busy, I'll be lucky to get time to do my weekly 50%

 

[corina savin]

Pond snails are not welcomed in a planted tank and an overpopulation might suggest overfeeding. A snail good for eating algae is the nerite snail but they lay eggs that are hard to remove and never hatch in freshwater.
Hornwort is a floating plant and it will thrive if there is minimum surface agitation.
Don't be afraid to remove old leaves from your swords, just snap them at the base so the entire leaf is coming out.
Check your phosphates levels including the tap water, you might have an excess. Try adding potassium as a fertilizer (it is a macro nutrient like nitrogen and phosphorous but seldom enough in fish food). If your nitrates are high, don't use Potassium nitrate, use Potassium sulfate.
Don't overfiltrate planted tank; plants alone can do a better job.
After you scrape the algae, make sure you vacuum them out (a lot of dead algae at once will seriously affect the water quality).
Above all, don't use chemicals to get rid of algae.

 

[Esahc]

I don't have a posphate test, but I'll see about getting one, and I'll test my nitrates and post that tomorrow and give my swords a good pruning while I'm at it.

is seachem potassium a good choice for potassium sulfate or can you recommend a cheaper/better option? In the meantime, should I try adding Flourish(which I already have and use for the upstairs tank)?

I'm working getting rid of my pond snails. I've added some MTS recently as well, in the hope I could at least have a useful pest snail once I find out how to remove most of the pond snails.

 

[Als49]

Since floating plants are not allowed and WC every other day is a stretch, how about:

1. Cover the side of the tank that get sun light with black cartoon? It'll help limiting the light.

My father in-law's tank also got algae problem due to direct morning sun light. He opted to use some commercial algae chemical removal and successfully removed the algae.

I prefer to not use any chemical in my tanks.

2. Adding hardy and fast growing plants such as egeria or fox tail? They are stem plants but they'll grow even if they're not planted to substrate. You can just let them float.

3. Remove the tank to somewhere safe from the sun light. This is the easiest solution if the space is available.