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Too Much Light?

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I have 56 watts (T5: 2 x 10 k, 2 x actinic) over a 15 gallon aquarium. I had no (little) algae problems until I did a massive tank re-planting; I exchanged about 50 % of the plants, disturbing 50 % of the substrate. Now I have green water. I don't use fertilizer or CO2. I use a 12-hour photoperiod.

I bought a 24 watt ultraviolet light sterilizer which is slowly treating the symptom (i.e. the green water) by means of clearing up the water.

My first question is: Do I have too much light?

I thought I didn't have too much because I didn't have any major algae problems before.

My second question is: When my plants get a foothold will they be able to hold off the algae?

Any help would be greatly appreciated.

- Jeff
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Fresh Fish Freak
24,398 Posts
Same thing happened to me- my mistake was I did a major replanting without doing a large water change immediately afterwards. When you disturb the substrate and plants that much you 1) send tons of nutrients up into the water column and 2) tend disturb the plants so they pause their growth a bit till they acclimate to the changes. That plus light = GW.

I suspect that once your plants get going again you'll probably be OK if they were OK before. I would probably reduce the photoperiod to 6 hours or so till the GW fades.

I just waited my GW out and it eventually went away on its own (8 weeks or so). If you start getting other algae once the GW fades you probably have too much lighting and too little CO2, though.

are you experienced?
1,989 Posts
thats alot of light not to have co2 or dose ferts im suprised the tank hasent been an algae problem before now! i guess the tank is loaded with plants. i have done total rescapes and took all plants out 29g tanks more than once with no problems with algae or gw. i guess i dont understand how removing plants could cause and algae bloom unless its effecting the bio load of the tank.
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