[hoppycalif]

Back to basics: Light is what determines everything else you do with an aquarium to grow plants and not algae. With a 125 gallon tank, no pressurized CO2, you have no choice but to go with low light and the plants which can do well with low light. Low light, using T5HO bulbs is far less than you now have. I would use half of the light you now have, and that might still be too much, even though some people have had good luck with even more light and no CO2 - those people are very much a rarity.

Plants don't need more than 10 hours of light a day, and 8 hours is really plenty, so I would reduce the lights on period to 8 hours.

Your plants should all do fine with that much light and that light duration, if they get enough nutrients. Enough nutrients means nitrates, phosphates, potassium, trace elements and a source of carbon. I would buy some potassium nitrate, mono potassium phosphate, and either CSM+B trace mix or use Flourish as the trace mix. Those I would dose per the EI method, only because it is very easy to do, but I would only dose about half the amount recommended for that size tank. For carbon, it has to be either pressurized CO2 or Excel. Excel might be adequate if the light level is low enough - very expensive, but adequate. You can buy those fertilizers from http://www.aquariumfertilizer.com/ or http://www.greenleafaquariums.com/aquarium-fertilizer.html and a few other online stores. Excel tends to be cheapest from either BigAls or Drs. Foster & Smith, during their sales, and in 2 liter or bigger jugs.

Last, why are you using RO water? Doing so makes it very hard to do weekly 50% water changes, which you need to do if you use the EI fertilizing method. If you feel you must use RO water, you probably will be happier using the PPS Pro method of fertilizing, both of which are described in the fertilizing forum stickies. If you use RO water you do need to add back the calcium and magnesium you removed - plants need both. You can buy calcium chloride and epsom salts (magnesium sulfate) to do that.

 

[hoppycalif]

i just ordered everything for the PPS Pro method from http://www.aquariumfertilizer.com
Our tap water is EXTREMELY hard, i can not adjust the PH. and i have soft water fish.

i am also really considering pressurized
c02. i have been buying the 2 liter juggs of excel and they last about a month. i'm also getting sick of buying 5lbs of sugar every week.

so if i cut back my lighting to half, what bulb combination should i use? the 2 5600 and 2 10,000? or 5600 and pink? i just reset the timer to 8 hours

also, i feed my fish beefheart & bloodworms once or twice a day. it all disappears in about 5 - 10 minutes. is this another problem?

You shouldn't be concerned with pH, only with KH. If you have high GH, that is good for the plants and invertibrates. In a fish only aquarium, you can use pH as a marker for most of the other potential problems with the water, but in a planted tank that isn't nearly as good.

You can chose the bulbs that make the aquarium look the most pleasing to you. The plants will grow with any combination.

One problem with discus, from everything I read, is when you try to grow them big by feeding heavily with protein rich foods. The leftovers can foul the water very easily. I have no experience with discus though, so others will have to recommend something for that.

What is the KH and GH of your tap water?

 

[hoppycalif]

The API KH test kit reads in degrees of KH, one degree for each drop it takes to get the color change. You seem to have 16 dKH tap water! Now that is very, very hard, and you probably do need to reduce it a lot for discus, or most any other fish. Most plants will do better with a lower KH, too, in my opinion.

I think you can do best using the PPS Pro method of fertilizing, so you won't need a lot of big water changes.

The time a tank of CO2 will last depends on the bubble rate. If you use the PPS Pro method, it seems that a low bubble rate, around 2 bubbles per second is all you would need. If that is the case, a 5 pound tank would last 3 to 6 months. The reactor you describe should work fine with pressurized CO2.

I didn't see anything about what filter you use. That is pretty important, especially with those meat eating monster fish. But, it should be something that doesn't create any splashing on the water surface, to avoid losing CO2 that way.

Your rocks that fail the acid test are why the KH in the tank rises, causing the pH to rise. They aren't suitable if you want soft water, unless you do big weekly water changes, like 50% or more.

 

[hoppycalif]

Are you using RO water, or water that goes through a softener? If the softener uses salt in it, it replaces calcium in the water with sodium, and that isn't good for plants or fish.

The Rena XP4 may not be big enough for a 125 gallon tank, especially one with discus in it. I hope someone with that size tank will comment on that.