The Barr Method

This is all quotes from Thomas Barr, edited.

Non CO₂ method

Thomas Barr: This is essentially the same thing Diana Walstad suggest. My only deviation is with the substrate, I use 1/2" peat and mulm with Flourite or Onyx has really proved wonderful in the non CO2 sets I've done. Otherwise, light is around 1-2 w/gal, generally I'll use a Triton(7200K), a small hagen HOB filter for current, lots of plants, a moderate fish load and feed them daily. I top the watwer off once a week and that's pretty much it except for the rare pruning. I add a lot of plants from the start. This is the most over looked thing people do when starting a plant tank. I use easy to grow plants mainly and work the hard to grow species slowly once the tank has settled down.

Substrate ferts make sense for non CO2 methods due to slow growth rates => supply = growth RATE

Non CO2 tanks can handle much more abuse and different fert routines since the RATE of growth is so slow, the lighting is less. Both of these make it possible to balance fairly well the fish waste production with the plant's growth RATE with no algae issues. Algae growth is slower (limited with CO2 and light), therefore herbivores can harass algae at a faster rate per critter adding less NH4. NH4 ratio uptake is very high in a non CO2 tank vs a CO2 enriched tank requiring less energy to Nitrogen uptake/assimilation into Amino Acids.

This was a goal of many planted aquarist back when I started keeping fish(1970's). Many fish only folks think that is what/should occur also. Seem plausible and logical.

I went back, removed all the fish and dosed small amounts of GH/KNO3, PO4 and a tad of traces 1-2x a week and had great results on a non CO2 tank also.

The volumes of dosing are smaller vs a CO2 planted tank. But this type of tank can be dine with little to no dosing other than fish food. Some plants might not fair as well if that is your sole source. Even a non CO2 tank can benefit from some dosing other than fish waste. talk by Thomas Barr on non CO₂ tanks

CO₂ method

CO2 enriched tanks make more sense using water column fertizers since growth RATE = supply, and the substrate will run out fairly quickly.

This method is popular with folks that still believe and cling to the mythical notion that excess nutrients cause algae in a well planted tank. There is nothing wrong with adding the nutrients in there though. But it's not to get around algae in any way. At high growth rates that are associated with CO2 enrichement, it is wise to dose regularly before a problem starts since the growth RATES are so high.

Due to this fast RATE of growth, plants run out of something very fast, then they stop/slow down growth, then you get algae. Add higher light, then it makes this even more critical. Much like oral hygine, do you wait till you have a cavity or do you brush your teeth daily? Maintenace of the nutrients is very similar. I've reasoned out a decent method to estimate the nutrients so you don't need a test kit even, Chuck's calculator helps the Chemically challenged.

Lower light CO₂ method

You can obtain a robust growth rate, not as fast as a high light tank, but a nice rate of growth and very healthy growth using low light and CO2. This gives the grower a nice middle ground so that they can get away with less water changes(if that is their goal), more wiggle room with dosing, more reliance on a substrate fert routine(if that is their goal), less light= less algae, less CO2 demand=> more CO2 wiggle room, more % of nutrients from fish, easier pruning schedule(less growth rate), less electricity and lighting cost.

This tank type bridges the gap for those folks that kick and scream about water changes, forget to dose, like substrate dosing, don't want so much work etc, but still have the nice plants associated with CO2.

All the plants essentially do fine at 2w/gal of NO FL's, add a reflector to that and that makes a nice easy to grow tank+ CO2.