Up until now, I've avoided use of Excel since I can't get it locally, and mail ordering costs a lot in shipping. But now that I'm going to start a saltwater tank, the cheapest way for me to get salt is to mail order it. So the additional cost that it would incur to buy Excel at the same time would be somewhat negligible. My 30g tank has diy co2, but it fluctuates a lot (between 10 - 30ppm); and more recently I've had repeated outbreaks of brush algae and I know this is why. Will adding Excel to this tank help solve this problem, even if the diy co2 continues to be somewhat sporadic? If I decided to stop dosing Excel, would I see any withdrawal issues such as when you stop injecting co2? Any other drawbacks to using Excel?

Hi Carissa,

While I am no expert, I definitely know that spot dosing of Excel helps kill BBA and prevent further BBA growth. You still need to prune the plants with dead BBA on it. The excel should help keep algae down. I don't know if it will keep the BBA completely at bay given the fluctuating CO2 levels, but it would definitely help.

As for withdrawal issues, I doubt you would see any given that your fert/light is optimized for a CO2 setup. The marginal increase in CO2 provided by excel, and the lack thereof when you stop is probably not going to be significant enough to cause any issues.

Excel does help to suppress algae, but I don't know if BBA is one of the types excel will help suppress.

I do have a couple of suggestions to stabilize your diy co2. Try using wine yeast. If has a much more stable fermentation rate and will last longer since wine yeast has a much higher tolerance for alcohol.

I put my yeast bottles in a water bath with a heater and small pump to help stabilize the temperature. This is more imprtant in the winter months. However wine yeast will ferment at lower temperatures. Temperature affects fermentation rates.

Use an efficient co2 reactor. I feel the best reactor is the forced reactor with a pump on top and sponge on the bottom of a gravel tube or bottle. Not pretty to look at but it seems to do a good job of dissolving the co2. Because of the small amount of co2 produced in a diy system the ability to dissolve co2 completly is important. The main disadvantage is you have to be careful of your water circulation. Misting has the advantage there. I always use an extra power head for more circulation.

Save yourself some money and use less sugar. One cup of sugar for each 2 liters of water is plenty. You could use a little more with wine yeast. Two cups of sugar in 2 liters of water will produce about 25% ethanol. Most yeast can tolerate 10% or less of ethanol. When the yeast stops producing co2 some people think the yeast need more sugar when it really was the build up of ethanol that killed the yeast.

I also use 3 liters of yeast solution per 20 gallons.


Henry

Good suggestions. I have tried to find wine yeast and haven't been able to yet, but I'll keep looking. I use a small desk lamp to provide heat, it really works great for keeping production going. My reactor probably isn't at 100% efficient, but it works well for distributing the co2 around the tank. It's an internal filter that has an inlet for airration, which I use for co2 instead. The impeller chops up the co2 into very tiny bubbles and then the output shoots them across the tank, this in addition to my hob main filter provides fairly good circulation, I keep my tank very full so the hob doesn't splash.

I find that I don't have a problem using up 2 cups of sugar in one 2L bottle, provided I add another tsp of yeast after a week or so (it seems that they run out of some nutrient or another after a week and slow down). How do I know it's being used up? I taste it before dumping it out. But if I add 3 cups of sugar, it will stop producing before the sugar gets used, and won't get started again. So I stick with 2.

My major issues with my diy have to do with either my not realizing it's slacked off quickly enough (out of town, etc.) or forgetting to turn the light on. For the first night after refilling, I can leave the light off, but after that night, I have to turn it on, or else it seems to slow down and not get going again.

Carissa,

If you add more yeast to the sugar then you simply achieve a toxic level of ethanol faster and the amount of co2 crashes faster. I use 1 tsp of yeast in 4 liters of water and 2 cujps of sugar. It lasts about 2 weeks. Larger containers will produce more yeast and therefore more co2. They take a little longer to ramp up so I mix my brew and let it cook for 24 hours before I hook it up.

The biggest problem with diy co2 is stability. In the case of bread yeast from the local store, what I observe is that there is an initial burst of co2, it then stabilizes, then drops. I have noted that after co2 production drops often times it will drop off to almost nothing in 24 hours. I think local water conditions will affect this. When I used regular yeast I changed the brew as soon as the bubble rate dropped. I don't wait for the drop checker to change color.

One other thing I forgot. I don't use a check valve. I raise the tubing above the tank instead. The low pressure of diy co2 with a check valve will cause production to drop off more quickly.

Henry

I only have 2 - 2L bottles. If I don't add more yeast after a week, the only alternative I have if I want to keep co2 levels high enough is to change out the entire bottle after one week. Since adding more yeast keeps it going for the second week, and it's cheaper and easier, that's what I've started doing. If I had larger bottles, or more of them, it would probably be a different story. It doesn't totally stop producing after a week, but just slacks to the point where my drop checker goes to a darker green. Then I know it's time to add more yeast. I try to stagger them - so that every week I'm adding more yeast to one bottle, and changing the other, this keeps the production stable and reasonably high. With 2 - 2L bottles, I can't let them go for two weeks without doing anything, my co2 levels just drop way too low, production slows too much.

My hypothesis that the yeast start dying off due to a lack of a nutrient is because I have observed that adding more yeast causes production to increase for a week. Therefore, the slack of production of the initial yeast can't be from ethanol poisoning, and can't be from a lack of sugar, or the second batch of yeast would also be affected; therefore it must be an nutrient of some type or life span that simply runs out to a large extent after a week.

I don't use a check valve either, I found that it would clog with water and stuff after a short time. I have a screw-in shut off valve that I just shut off when I'm removing a bottle to ensure the water doesn't back-siphon. The rest of the time, it's a closed system, so water can't back siphon anyway.

I think co2 gas is the best investment i've made in this hobby. in fact if I see more bba than a couple of shrimp can handle, I am certain to be low on the stuff.

Sherry you are right. I do have pressurized equipment, but for tanks up to 30 gallons and low to medium light I do use diy.

Carissa my yeast lasts 2 weeks because I use wine yeast. I've used bread yeast and co2 production drops off significantly after one week. On day 6 I start a new bottle and give it 24 hours to get going and then change bottles.

After you add yeast how does the co2 production compare to a new bottle ?

You mentioned that your co2 levels varied from 10 - 30 ppm. That does not sound stable. I would be really surprised if anyone could maintain a stable level of co2 for 2 weeks with bread yeast under almost any conditions.

Some of my information came from the Aquatic Gardeners website. There is some information on diy yeast provided by Tara Nyberg who I believe studies yeast for a living. It's worth taking a look.

BTW I love koi angels. I have some in my 50 gallon.

Henry

There is a bit of a difference in production between when I have a new bottle and when I add more yeast. With a new bottle, the production is such that I'm really wasting it - some bubbles are coming out too big and going to the surface and breaking right away. But that's ok, because my drop checker turns a light green. So it's really overproducing at first. Then it seems to level off for about four or five days where my drop checker is a stable green. After the sixth or seventh day, the drop checker starts to go a bit darker, not blue but getting in that direction, then it's time to add more yeast (if I do this right away, I don't have bba...if I wait too long, that's when I get trouble). After I do this, I get massive overproduction once again, but it only lasts for a few hours this time, then it settles down to a stable green color again for another week, give or take a day or two. Then if it starts slacking again, I just change out the whole bottle.

That's all being said as if I did both bottles at once, not staggering them (which I have done sometimes). If I stagger the bottles, I get a more stable production. I guessed 10 - 30ppm, not because I can't keep it more stable than that, but because in reality, I occasionally don't recharge my bottles on time so it drops down to the 10 level. But if I keep on top of it all the time, it probably stays around 20 - light green to green on my drop checker. As long as I keep up to the green level, going higher doesn't make much difference. It's only when I go into the darker green that I have trouble. My problem is that life gets away from me.... and suddenly it's been two weeks, and I haven't done any bottle maintenance. I only have 2wpg so it's a little forgiving.