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Green Spot Algae on Plants!

7968 Views 11 Replies 4 Participants Last post by  mistergreen
Hi Guys,

I have a 125L tank thats been cycled for about a month now with 3 well established Anubias plants on driftwood. However, when i transferred the plants from my old tank to the new tank about 6 weeks ago they quickly developed GSA.

Here are my tank parameters:
GH - 5 - 6 dh
KH - 2 dh
PH - 6.8 - 7
Phosphate - 1.5 ppm
CO2 - 0ppm
Ammonia - 0 ppm
Nitrate- 0.25 ppm
Nitrite - 0 ppm
Lighting - 2 x 14watt led tubes

I have tried everything possible to bring it under control but it continues to grow. I cut out the use of flourish ferts all together and started dosing excel daily, as required. I upped the phosphate to around 3ppm (along with magnesium and potassium dosing) and cut the lighting down to 4 hours a day for 3 weeks and still nothing, i even added nirite snails to the tank and they didn't even bother with it. In the past week i have kept a sheet over the aquarium to cut out all ambient light and Im still noticing GSA growth. My Anubias plants have also been growing very quickly since, so the treatment is working on the plants just not the GSA. Today I've resorted to taking out one of my pants and putting it in my 40Litre tank with very mature bacteria and Im hoping it will begin to subside. Im not sure what else i can do but any advice would be greatly appreciated!

Here is a link to some photos, they are not the best at showing the extent of the GSA but at least they offer an idea. Thanks!
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Slow growing plants tend have algae grow on them. Try adding more faster growing plants around the anubias to shield it from the light.
Welcome to APC! I like the aquascape you have, but I agree with mistergreen that having some fast growing stem plants would help discourage the algae. I have found that anubias plants are very hard to keep algae-free, except on newer leaves which are still growing. They are not easy plants to keep growing well, in my experience.

It is hard to know how much light you have from just the wattage. Do you live in an area where there is an aquarium club that loans out a PAR meter? That is the best way to know how much light you have. What brand, and model, are the two LED tubes?
Thanks for the welcome and quick reply! I think thats a good idea putting some extra plants around the anubias, ill be sure to give it a try. Next time I head to the aquarium specialist i might ask them about the lighting meter but they are 'juwel multilux' 80cm led tubes. Ive had BBA and GHA before and usually they clear up after a couple of weeks by double dosing excel but this GSA just wont quit. Even with a halved photoperiod it continues to spread. But I've had these plants for over a year in another tank setup and i never had a problem with algae on them, only when i moved them to the new tank did the algae take over.
I found that double dosing excel daily isn’t as effective as 5x dosing after weekly WC in controlling algae. If you are dosing 5x weekly, you do not even need to dose daily unless you want to provide a carbon source.

Dead algae don’t fall off by itself. Get a troop of bristlenose pleco will also help to clean out the dead algae and prevent new algae to take root.
Whoa, 5x dosing is extreme. I've killed a few fishes and moss with a little over 2x.

I've given up on fish as algae control. As they grow older, they depend on fish food and leave algae alone. The best algae controllers are snails and shrimps. I hear amano shrimps are the best and they'll eat BBA too.
5x after WC is recommended by SeaChem, not extreme for fish. Toxicology studies have shown that adult fish can tolerate even higher levels than 5x, though invertebrates, mosses, Val’s, fish eggs and fry are more sensitive and may not survive. I’ve been dosing 2x daily for a year and I couldnt get rid of some persistent bba and gsa until I switched to 5x after WC. One notable indicator is that I had some mosses that hitchhiked into my tank that I couldn’t get rid of until I switched to 5x dosing. For any medication, under dosing below the therapeutic level won’t work and may even be harmful in cultivating drug resistant strains.
5x after WC is recommended by SeaChem
Oh, you're talking about the recommended dose. Not 5x the recommended dose. To be more clear, Seachem recommends 5ml per 10 Gallons after a water change and 5ml per 50 gallons daily.
Oh, you're talking about the recommended dose. Not 5x the recommended dose. To be more clear, Seachem recommends 5ml per 10 Gallons after a water change and 5ml per 50 gallons daily.
Yes, thats what I meant. SeaChem recommends two dosages, one for daily and the other after each WC. The after WC dosage is 5x the daily dosage.
Just an update on the tank. After doing a butt tonne of research online I think i honed in on the reason why the GSA was so persistent. Im fairly sure it started because of low phosphate but hung around because of excess micro and macros in the tank. So yesterday i turned my pressurised C02 system back on to increase the uptake (I originally turned it off because the regulator is very touchy and i was worried about starting an algae bloom with the added phosphate and irregular C02) I then started spot treating my young anbias plants on the driftwood branch with pure excel. Since then I haven't noticed any new growth on the glass or new leaves which is good, however, the larger plants are still overrun with it. So today I just decided to a 2 minute bleach dip on one of the large anubias and bam! The GSA is gone! ill do the other plants later in the week depending on the state of the first plant and hopefully with the C02 running it will keep the GSA from spreading, fingers crossed! Thanks for all the suggestions though, Ive got shrimp in my tank too btw so ill steer clear of the 5x dose. but like i said, the spot treatment seems to be working. Heres a photo comparison of before and after the bleach, i wish i had taken a better 'before' photo to show just how much GSA was on the plant, but oh well. Shot 2018-10-06 at 9.18.24 PM.png?dl=0
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It’s much safer to spot spray with 3% peroxide on exposed algae during WC when the water is lowered. Any spill over won’t harm fish as it turns into O2. Bleach is not safe and residue can kill fish if not thorougly dichlore. Peroxide is as effective as excel but costs a lot less.
Be careful how long you expose the leaves to excel, peroxide, bleach. I find over a minute will melt the anubias leaves over a few days (not immediately). I expose it for like 20 seconds and wash it off. Peroxide is safest and cheapest.
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