I have been running my 50 gallon for about 6 weeks with one 2 liter bottle of a yeast and sugar mix for CO2. I am please with the results. I am just wanting to gather thoughts on adding another bottle to the mix. I would most like change each one once every 7-10 days. Would this be a good idea?

if you have the time and patience for that much hands on and maintenance - then yes, i have read that on the bigger tanks, such as that one, two 2 liters are recommended.
i dont have any personal experience with this set up but i spent a few days worth of time researching it when i was considering it.

on atank that big, i would go with gallon size jugs.i used a set of two gallon size jugs hooked up in series for a 55 that i had setup and it worked great. plus the bigger jugs give you a longer life on the yeast colony because the solution does not toxic as fast.

I only got really good results when I upped to 6 2liter bottles on my 40 breeder. I have them plumbed in line in pairs and change one pair per week. Plumbed with check valves so as to not lose pressure when disconnecting bottles. I'm actually going backwards now and weaning my plants off it and going back to metricide in preparation for a 125g build that will not have real C02.

Sent from my LGLS990 using Tapatalk

It's always better to have multiple bottles with staggered start times, in order to maintain a consistent rate over time.

I recently began DIY on my 75 gallon. Started out with 3 two liter bottles, staggered one week apart, changing out one each week. The recipe Im using lasts two weeks before starting a slow decline. I got dramatic results at first, but as plant mass quickly increased, and fert levels were adjusted to meet the higher demands, I soon found that I wasnt getting enough Co2.

I decided to add a fourth bottle, combine them in pairs, and change out 2 per week instead of one. In theory that should almost double the output. Instead of always having two bottles full strength, and a third winding down, there is now 4 bottles running full strength, all the time. I also wound up going with 3 liter size instead of the 2Ls. More water = more Co2, for a longer period of time, as someone pointed out above.

The difference has been astronomical. Drop checker went from dark green to light lime. Plants pearl like crazy now, before there would just be a little bit near the end of photo period.

Here is a build thread I made on the system. You may get some food for thought. I havent gotten around to updating it since going to four bottles - https://www.plantedtank.net/forums/sh...d.php?t=659290

I have two 2 liter setups. One on my 50 and one on my 10. I don't really have a place to add more than 1 more bottle to the mix. I think my husband will kill me too. I am planning on going pressurized which I should be able to use 1 unit to dose both tanks. I just wanted to increase the the amount of CO2 a bit. I didn't think it was going to be hard since I can easily get another bottle. I have a T valve to splice it all in together. Would I absolutely need a drop checker if I added the second bottle?

You dont need a drop checker at all really. There seems to be considerable debate over their accuracy in the first place, or at least in their ability to indicate specific concentrations. I just like being able to see a reflection of changing levels at a glance, plus I think they look cool. But there is literally zero chance of gassing your fish on a tank that size using diy yeast/sugar.

diy pressurized setup adds up to ~100$. you really should consider that.

I am considering that but I have been out of work for 6 months and the husband would kill me if I spend $100 on the fish tank and then tell him I have no money for the car payment.