CO2 sparks thread/string algae explosion
 

I recently installed a CO2 injection setup on my tank, and immediately (as in, within a day or two) had a massive explosion of thread or string algae. Aside from the algae, the plants are doing wonderfully! I've noticed growth spurts on everything in the tank.

http://i.imgur.com/64uwMl.jpg

I've done a little bit of reading, and people seem to blame these kinds of algae outbreaks on too much lighting. I'm coming from saltwater, where the issue is always insufficient lighting, so it's entirely possible. I had 4 24W T5s (from an old reef setup) on this 10gallon system, but I've gone down to 2 in the hopes that this will reduce the algae.

I'm fine lowering light levels to combat algae, but I want to make sure I'm not slowing my plant growth at the same time. Are there any tips on how to do that?

So if I understand you correctly the tank was running the 4x24 without the co2 initially?

That's right. It's a new tank, but it ran for about a month with those lights and without the CO2, with very little algae. Adding the co2 was definitely the catalyst for the algae bloom.

Are you dosing any ferts?

No I'm not. I'm using aquasoil as a substrate, but beyond that I'm doing doing any fertilization.

Are your T5's HO or NO? Can you drop it down to one bulb?

If I understand correctly you need a balance of lights, CO2 and ferts. If any of the above are out of whack you get algae. Seems as if you have high light, CO2 and no ferts so the plants use what they need and then the algae takes the rest and runs with it. Definitely still a noob here but I think you need to either greatly reduce lighting or add ferts to achieve balance.

Creekbottom: They're 24", 24W bulbs. I believe that's HO. I can't run a single bulb.

That doesn't seem right to me. Light isn't something like a nutrient in the water that a plant can use some of, and algae gets the rest. The plants and the algae are seeing the same light level. It may be that there's some light level where the plants will survive and the algae can't, but it isn't a matter of (Total light) - (Amount used by plants) = (Light growing algae). I suspect adding fertilizer would cause an even greater algae explosion.

Does it make sense to throttle the CO2 back instead? My gut feeling is that I've eliminated CO2 as a factor limiting plant growth, so my main drivers are the nutrients in the water and the light. If the plants are able to outcompete algae at a lower CO2 level, maybe it's worth trying to find that level rather than reduce light. I'm worried I'm going to stunt plant growth if I throttle the light back too much.

How much co2 aree you injecting, and how? And for how long?

I'm fairly new at this as well, but I've had my fun battling algae and it's finally on the way out. With those two bulbs running on a 10 gallon tank, you pretty much have the sun right above your tank. You currently aren't adding enough CO2 and ferts to help the plants out-compete the algae.

I would shade that light, or lift it up. Window screen works well, or get some floaters. Probably both.

Unlikely, It takes a while for algae to really develop before it becomes very visible and a nusiance, probably just a timing thing more than anything else.

A tank isn't like a jigsaw puzzle where you can add pieces as you go along. You have aquasoil and high light without co2, that's a algae incubator, it just had to develop.

BTW any stirring op of the aquasoil will realize ungodly anounts of ammonia etc into the water column so if you did that it would certainly make it worse.

I would do lot of water changes, trim, cut lights back to 4 hrs, use carbon or other organic removal media and yes use co2.

I was watching the tank pretty closely immediately before and after adding CO2, there's no doubt in my mind that before I added CO2 there was little to no algae, and a huge bloom immediately after. Maybe the CO2 accelerated the growth of algae and plants alike and just brought about an inevitable bloom sooner, but the change was really rather dramatic.

I'll try reducing the light/co2 cycle to fewer hours per day and see if that helps. I've already reduced the CO2 flow, but I can bump it back up if it would help. I was at ~2 bubbles/second, and reduced to 1. I'll look up the model of my bubble counter if people want to do a real comparison, I'd imagine the numbers don't translate between different models.

I wish you luck, but you would be probably the first that reduced the co2 duration to only part of the light duration and solved their algae woes. It just doesn't work that way and I've been doing this a long time. Good, healthy growing plants will out compete algae all the time as long as there is enough of them. Tanks with high-light and no co2 become algae farms sooner or later. When something is in short supply in this case co2, the plants won't grow as well and algae has no problem in that environment.

I have the lights and the CO2 on the same timer, to avoid PH drops at night when plants aren't photosynthesizing. It's easy to change though. That's why I said light/co2 cycle, it's the same thing currently.

I'm fine with bringing the CO2 back up and reducing the photo-period, but if the point is to have the plants outcompete the algae maybe the solution is to leave the lights, and the high CO2 and simply add more plants.

I'm sorry if I come across as resistant to reducing light, this is the first planted tank I've tried after many years of reef tanks. I'm used to more light always being a positive.

This is a good start, look into some dosing regimes as well.