Low-Tech Excel based Planted Aquariums: A Guide

Non Co2 Low Tech Planted Tank

Before reading this article, I would highly recommend that you read the article on Low-tech, Non CO2 tanks. That article introduces the concept of low-tech tanks and explains in detail the science of low-tech, non CO2 tanks along with some guidelines for maintaining such tanks successfully. One of the drawbacks of this low-tech method is that plant growth can be fairly slow compared to growth rates seen in CO2 enriched tanks. On the other hand, tanks with pressurized CO2 require you to invest a fair bit of time and money to keep them in shape. The balance between lighting, nutrients and CO2 in these tanks is much more delicate and there is a lot less room for error. Any imbalances in the tank can quickly lead to a massive algae bloom. This article details a middle ground between these two methods wherein Seachem's Excel is used as a source of carbon in the tank.

Seachem Flourish Excel

What is Excel and what does it do?

The active ingredient in Seachem Excel is Polycycloglutaracetal. It is a clear liquid which is quite toxic. Be careful when handling it and make sure to avoid skin/eye contact. Essentially it is a Carbon compound which is assimilated by the plants and used by them during photosynthesis. In this manner it acts as a carbon source and a replacement for CO2 in planted tanks. However the uptake of Excel is not as much as dissolved CO2 in tank water. In lay mans terms, it takes "more work" for plants to use Excel as a carbon source than it does to use dissolved CO2 directly from the water. As a result, while Excel does boost plant growth in comparison to Non CO2/Non Excel methods, the growth rates will still be slower than in CO2 enriched tanks. Also note that Excel has a half life of 11-12 hours so it is not active in your tank beyond 24 hours. This is why daily doses are recommended. Also make sure to dose it before your light come on in the tank. Excel is light sensitive so make sure to store it in a dark bottle if you plan to pour it out of the regular bottle.

Advantages of using Excel:

1) Faster plant growth as compared to Non CO2, non Excel, low-tech tanks.
2) Excel is known to act as an algaecide. Many people dose excel in their tanks when they are battling algae and have had great success. What this means is that the daily dosing of Excel will act as a deterrent to algae. This is great news for anyone starting out with their first planted tank.
3) Much easier to use in comparison to setting up a CO2 system.

Disadvantages of using Excel:

1) Excel works great for smaller tanks but it can get pretty costly for larger tanks.
2) Some plants which do not have stomatas cannot be grown with Excel. This includes plants such as riccia, vallisneria, egeris densa, hydrilla and liverworts.
3) Excel is toxic. Be careful when handling!
4) Fertilizing is a must for a healthy tank.

What changes when you use Excel in your tank?

Here I'm going to talk about what you need to do differently in comparison to Low-tech, Non CO2, Non Excel tanks as described here. The main effect of adding Excel is that you boost plant growth rates. As a result it also causes a larger demand for nutrients by the plants. The availability of a carbon source allows us to increase the lighting levels by a bit in comparison to non excel tanks. I will list the changes that need to be made in comparison to the guidelines for non excel tanks.

Lighting: Lighting can be pushed up to 2.5 watts per gallon (wpg) at max. You probably don't want to go any higher than this. As before, in the case of spiral CFLs you could probably go up to 3 wpg due to their inherent inefficiency. With T5 tubes you should probably stick to 1.5-1.75 wpg. If at any point you see signs of algae (assuming you are dosing ferts normally), then you should immediately lower your light levels/lower the length of photoperiod or do both. Remember that playing it safe with slightly lower lighting is always a wise choice as you will have less trouble with algae on the whole. Also remember that for tanks smaller than 10 gallons, the wpg rule breaks down. You'd probably need 5-6 wpg for tanks that are 5 gallons or smaller.

Dosing fertilizers and Excel:
A 20 gallon tank using excel should get:

  • 1/8 teaspoon of KNO3, 1-2x a week
  • 1/16 teaspoon of KH2PO4, 1-2x a week
  • 2mls of Seachem Flourish, 2x a week
  • SeaChem Equilibrium 1/8th once a week (Immediately after weekly water change)
  • 50% weekly water change
  • Dose 1-1.5x the recommended dose for Seachem Excel (1 ml for every 10 gallons on a daily basis and 5ml for every 10 gallon after 40% or more water changes).

As you can see the fertilizer amounts are higher than in Non Excel tanks. Also now it is recommended to perform 50% weekly water changes. The reason for this is that over time the excess nutrients in the water will start to build up. As a result we need to use the weekly water change to "reset" the system and bring down the nutrient levels in the water. It also helps maintain the water quality in the tank. Once your tank is well established you can try doing water changes maybe once every two weeks. Also if you are dosing leaner than recommended (with no visible signs of nutrient deficiency in the plants) then you could even try doing water changes once every month. However make sure to at least do them once a month if not more regularly.

1) Dosing ferts as recommended above
2) Occasional pruning to ensure good circulation in the tank
3) Gentle gravel vacuuming on occasion to get rid of excess detritus (never do a deep gravel vac)
4) Feed fish every day
5) Do a major (60-70%) water change after any major pruning/rearrangement which involves uprooting plants and moving the substrate around.

As you can see, we do not skip dosing ferts once a month as recommended with non excel tanks. This is because we are now doing weekly 50% water changes to keep the nutrient levels in check.
All the other things mentioned in the non Excel tank post regarding Fish, Substrate and Planting remains the same for Excel based tanks. That is pretty much it. So what are you waiting for? Get started on your aquascaping you planted tank fiend!ย  :mrgreen:

Acknowledgments: Most of this article is based on all the useful information I have gleaned from scouring through the forums at Tom Barrโ€™s site, . He deserves credit for a lot of the content in this article. Iโ€™ve just put it all together in one place and added some more stuff to make this more accessible to the planted tank newbie. The original thread related to this technique can be found here : .

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48 thoughts on “Low-Tech Excel based Planted Aquariums: A Guide

  1. That article was exactly what I was looking for. Thank you so much for taking the time to write down your findings/experiences and share them with the rest of the world. I am just starting with a planted aquarium, and I look forward to trying your methods. I just bought a 500 ml bottle of Excel a couple days ago.

  2. Very helpful to me. I wish you would have included on either of your articles, guidelines about water, as let’s face it, it is definitely a factor. For instance, as most of the rest of my state which is mostly rural, we have a well with high silicates, calcium, and ph, so we have a softener. We have had it turned off for two months for the tank, but that can’t continue. Are your dosing instructions the same whether using RO or using tap? I can’t seem to find anyone who discusses that.

  3. Believed the numerous comments on the effects of overdosing with Excel and did not try. 50% water changes have caused me more problems than anything. My tank, with Vals, gets 25 % changed every other week or so to prevent the chemistry changes from shocking my Denison Barbs which are from 7 to 4 years old. Yup, lost a few in my school to a 30+ % water change while the water department was adjusting the water chemistry as it battled the Micro Cyst in Lake Erie. Started at 1/2 dose daily and at water change, increasing to full dose at the third water change (after 4 weeks). 8 weeks now. So far the mossy algae is disappearing and new shoots are sprouting from the Vals. Tank looks great. 55gal overstocked with fish but has quite a few plants, which were flourishing for years. Most fish are over 9 years old, a Clown Loach is close to 13 and over 6 inches long. Saving pennies for a bigger tank and a matching gift for the wife ๐Ÿ™‚
    Excel has made a big difference.

    1. Glad the Excel is helping out. For smaller tanks, It’s hard not to use Excel because it does help with plant growth a lot and enables growing some neat plants that would be difficult to keep alive with a purely low-tech tank. The algae fighting tendencies of Excel is just extra gravy! ๐Ÿ™‚

      1. any chance (for a beginner dummy reading lots while trying to keep my plants alive) you could list the ppm we’re shooting for in this setup like you did in the low-tech non-excel article? ๐Ÿ™‚

        1. Sorry for the late reply. It’s been so long since I thought about ppms. Unfortunately, the couple of dosing calculators I used to rely on seem to be offline so I don’t have an easy way to give ppm numbers at the moment. If you find a good dosing calculator (some of the planted tank forums should likely have such calculators), then that should easily do the conversion for you.

  4. Water is hard as a rock, 7.0ph, moderate alkalinity. I use a lot of dolomite and peat in the substrate to keep the water buffered against ph shifts caused with the water changes. That new 120gal tank will have a constant feed from my RO unit and a drilled overflow with direct drain to our sump for constant water changes and then just daily dosing.

    1. Good catch! The main reason is that the non-excel approach assumes less frequent dosing on average whereas with Excel you want to stick to a weekly schedule. That being said, there is a lot of forgiveness when it comes to traces so either number would be fine as long as you are topping up traces from time to time. Cheers

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