Excel dosing, a middle ground for aquatic horticulture methods

Tom Barr

Staff member
Jan 23, 2005
Bridging the gap between the methods and each of their perspective trade offs is a challenge for many aquarist. There has been some confusion surrounding the use of Excel, a product made by Seachem Laboratories and which method to use for this.

The first real issue in the trade off is to understand that Excel will radically increase the rate of plant growth. Not like CO2 by any means, but a lot more than a traditional non CO2 approach. This means that adding supplemental fertilizers might be required, particularly with light fish loads/feedings.

The biggest advantage to using Excel is really allowing the aquarists to use water changes versus a traditional non CO2 approach which discourages water changes.

This may be done weekly, once every 2 weeks, or monthly at 50% or 25% etc. you may also use test kits to determine when a good water change is required based on NO3 build up.

Often times, aquarists want to not hassle with as much gardening, nor deal with CO2 systems and higher light, nor frequent water changes, but not go so far as to avoid them altogether.

This allows aquarist to keep higher fish loads, less pruning and algae, fewer water changes, but still have a nice looking aquarium with a wider range of aquatic plant species.

Negative Trade Offs:

Excel is toxic at higher than recommended label rates. Some get over zealous and kill their shrimp and fish. Cost: it can become costly over time and with larger aquariums. Needs dosed often, not a big issue if you add fish food often as well, dose the Excel when you add food etc. More pruning requirements, this might be good and bad depending on who you ask.

I do not think using Excel should be viewed as non CO2 methods, it has more in common with traditional CO2 enrichment methods, so those methods are more applicable overall. While not a gas when you add it, it does turn into fixed carbon, so the aquarist is enriching their tank with carbon fertilizer.

I think there is about a 250-300% increase in growth using Excel compared to non CO2. There is about 1000-2500% increase in rates of growth using CO2 gas.

So Excel is about 1/3 or thereabouts that of CO2 dosing.
So the nutrients can be adjusted relative to that for CO2 vs Excel dosing.

Note, using sediment enriched sediments like ADA' s aqua soil are beneficial with Excel and allow water changes for the first few months/weeks. Then very little dosing is required other than perhaps some traces, feeding fish etc. Many CO2 gas aquarist want this type of dosing routine, but often have more trouble using CO2 gas and complaining about pruning, algae and other issues. This method can help, but also, this is true for all methods, using less light will reduce the amount of work, maintenance and rates of growth, making the aquarium easier to care for and less prone to algae.

Using Excel is no different. Many try to use Excel as an easy way around having to use CO2 gas and then make a really bad assumption: more light is better.

Both CO2 gas and Excel do exceptionally well with relatively low light, say 1.5-2 w/gal using T5 light is plenty to grow any species in typical shaped aquariums.

Still, using Excel, aquarist should stay at 2w/gal or less for their lighting. Some get away with more light, but as you add more and more light, you increase risk of algae and plant health issues. Stick with the middle ground lighting or error on the lower side, plants will still grow and be easier to manage, which is often why everyone dose not use high light/CO2 :p

You may not have the goal to grow aquatic plants as fast as possible.
So control the rates with CO2, non CO2 or Excel and mostly with light.

Tom Barr