Looking for alittle advise on a 90G planted tank I am setting up. Alittle about the tank..flourite substrate and I have 4x54w of T5Ho available for lighting and am planning on a fairly heavy plant load. It comes down to this...CO2 or excel as a carbon source and the catch is I work out of town numerous times in the summer for up to a month at a time. I would love to have the growth and beauty of a co2 tank, but is it possibl to leave it unattended for 30 days at a time? (Gf will be there in case of emergency, but knows nothing about aquariums!!) Could this work if i used a fert doser or 2 maybe, one for macro and one for trace? could it work with 4 weeks between water changes ? Or would it be better off going with excel and hoping the tank will turn out ok. Thanks alot!

In that situation, if it was me, I would go low-tech. High light like that can cause problems to occur really fast if something goes awry. I would be afraid to leave a tank for a week with lighting like that, much less a month, and that with no water changes. A non-co2 or Excel tank with low light (maybe half what you have there) and a rich substrate will be much more forgiving. A month is a long time for any tank to go without water changes, much less a planted tank and high-tech at that. My .02 anyway. Non-co2 tanks can be very nice, without nearly as much hassle. The lighting is the issue here I think, that determines the speed at which things take place.

I agree with most of the above, I think CO2 is out of the question. You could use excel when your around. Also turning the lights down to a reasonable amount of hours while your gone should help.

I'm not sure that that light would be too much? but maybe you coulds only run 2 bulbs while your gone?

Effectively you will have over 3 watts per gallon on that tank, far too much for an Excel only tank, and equally far too much to leave the tank unattended for 30 day periods. You would almost certainly return home to an algae filled mess the first time you left it. It is work and it can be tricky to use even less light than that, observing the tank every day, cleaning it weekly, doing water changes weekly, and hoping to get a good result. I agree with Carissa that you would be much happier with a no-CO2, low light tank, where everything happens over a much longer time span. Even then, 30 days is a long time to leave the tank unattended, except by an uninformed, un-motivated "helper".

I have to agree with the other replies, that a low tech, low-light setup would be better for you.

With high lighting and c02, you need to fertilize. With ferts, you need water changes.

I would go to 1 or 1.5 watts per gallon. See if you could mount the lights so that you can raise them a few inches when you are away. That will reduce the growth and nutrient requirements and make it a little easier.

I agree the co2 is pushing it for this set up!! but It would only be 2.4 watts per gallon, which I dont think is too high, considering the 24in depth?? Im debating using the full four bulbs for maybe ony a few hours a day? Might work with excel?
And sorry but I really dont understand this unmotivated, uninformed helper comment?

Thanks for the help

Because you have T5 lights, I assume with individual reflectors for each bulb, you have at least 1.3 times more light per watt than the watts per gallon "rule" is based on. Possibly more than 1.5 times more light. So, the 2.4 watts per gallon is effectively at least 3.2 effective watts per gallon and possibly more than 3.6 effective watts per gallon. The depth of your 90 gallon tank is about what is normal for that size tank.

If you have someone looking after the tank, who is well versed in how to care for a high light tank, and well motivated to do the work involved, then you aren't really leaving the tank unattended for a month. But, from your description your "helper" doesn't know how to care for a high lighted tank, and, as a result I doubt that she would understand or be very sympathetic to the need for routine maintenance, pruning, cleaning, etc. that such a tank has to have. Undoubtably you could make this work, but it will be much more likely to succeed with lower light.

I got you now, The tank is going to be low tech so it will require minimal attention when im gone. I've had lots of success leaving fish, and expensive picky ones at that, alone for long periods of time with just some one feeding them daily and they are very healthy. I think I can now make it work for a planted tank! I can set it up so it only requires weekly, or twice a week ferts only. I will be home now untill next summer so theres lots of time to get it up and running and stable.

The lighting I have is actully two 2X54w lighting fixtures with parabolic reflectors if that makes any difference.

Im still planning on using excel also. Could i use a doser for that and lower the dose and the lighting when im gone?? Just to slow it all down?

Also I will be using flourite for the substrate as I already have 6 bags of it sitting at home. I am going to use Leonardite as a first layer. How much should I use? I can by 1, 3, or 12 pound bags for between 12 and 65 bucks CAN.

And for plant load....whats a good number of plants to give me the best chance at success? I was thinking 50-65 to start?

Thanks for the help again

Also would I get better results with the dry ferts like KNO3, KH2PO4, AND K2SO4 or using seachems line of ferts?

Or is it just the price thats the advantage?

"Low Tech" means low light intensity. You can't successfully reduce the plant growth rate by restricting fertilizers. You can only do that by restricting the light intensity. If you use only one of those two light fixtures you will have a chance to succeed. To do that I suggest reading about Diana Walstad's "el natural" method for running a planted tank. One place to do that is http://www.aquaticplantcentral.com/forumapc/el-natural/.