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Re: Hybrid substrates

Justin Collins is wondering about the substrate in his new tank -

> At the risk of setting off substrate wars round XXXXXVI, I'll ask this question.  I'm assembling the stuff to set up my new 100 gallon, which will have CO2 injection, substrate heating cables, 280w of VHO (to be upgraded to 350w of suspended halides within a year, most
> likely), and a well sealed sump (I'm going to experiment with having very little biological filtration.  If it doesn't work out I'll use a small wet/dry).  My question is about the substrate.  Now this may be the worst idea anyone has ever had, but I have 1000 grams of
> Duplarit G I plan to use in the bottom 1/3, as per instructions, and I am wondering if any benefit can be gained by mixing in a small amount of peat and/or worm castings.  Not nearly enough to qualify it as a soil substrate, but enough to add more nutrient value and CEC that
> the plants can access.  Any thoughts?

Yes Justin, I have some thoughts on your substrate plan - most of them negative, but based upon personal experience.

A little over two years ago, I set up a new 120 gallon tank. It has 525 watts of 5,000K Metal Halide lighting and very good filtration and circulation from an Eheim 2260 (overkill, but I had it in the closet). I had read "The Optimum Aquarium", the KRIB, the FAQ's, and
everything else I could get my hands on. I had also used Dupla products in the past with excellent results, and had also used peat and other materials in my substrates with generally good results. But I wanted "something different", "something better". I fell into the trap of
"if x, y and z are good on their own, then x+y+z must be fantastic!" My substrate consisted of Sera Peat Granules, Dupla Duplarit G, and Aqualine Buschke Terralit all mixed with gravel as the lower 1.5" level of the substrate. I had placed an epoxy coated heating manifold on the
bottom of the tank before I added this rich lower layer. This was all covered with from 2" to 4" of plain granite gravel.

Aside from problems with the Metal Halide ballasts (I'll never buy Energy Saver Unlimited pendants again), the tank had and continues to have problems with a lot of plants due I feel to a too rich substrate. A lot of plants just _won't_  grow in this tank, while I can manage to
grow them quite well in other tanks with simpler substrates. Those that won't grow just tend to rot off at the gravel level. The tank has also had a lot of algae problems, even though I use R/O water.

I'm rapidly coming around to a personal conviction that the KISS principal is every bit as important to success in this hobby as Dupla's 10 Golden Rules are. I'm faced with the prospect of removing almost 350 lbs of gravel from this tank and re-washing it and then having to
re-set the whole thing again, this time using Duplarit G at Dupla's recommended rate. No more complex substrates for me, at least not in a large tank which is a focal point in my living room.

Incidentally, the heating manifold will be going into the recycling bin (it's epoxy coated copper, and no, there is no leaching of copper from the manifold - I test constantly for copper in the water and in the substrate using a LaMotte Copper Test Kit and have never gotten a
positive reading) - I was able to measure a definate heat gradient in the substrate using the manifold, but could never see any positive effect on either plant growth or tank stability. The design of the manifold closely followed one which was described several years ago in an
article in AFM.

I'd recommend that you use Duplarit G alone (or Terralit, again alone) in the bottom 1/3 of your substrate. All the talk about increased CEC seems to be more conjecture than fact, at least to my mind.

As for your decision to go with minimal biological filtration, I can't argue with that - a well planted tank can deal with a moderate fish load all by itself. But I would recommend that you have very good water circulation in the tank. The pump in my Eheim 2260 is rated at 2280
L/hr and produces one heck of a current, but I have it split thru two separate inputs into the tank and I found that the circulation in the six foot long tank was not sufficient, especially as the canister loaded with detritus. I now have an auxillary Eheim 2252 Power Pack
filter unit in the tank (1200 L/hr) and the leaves of the plants which DO grow well in this tank (and a lot of plants do quite nicely) are in constant motion, waving gently back and forth in the current. The fish seem happier with the increased current in the tank as well,
schooling in tighter formation and constantly on the move, with better colours and larger appetites The fish do breed constantly, so they must be happy..

> The second substrate question I have is that in my 60 gallon I am using a 50/50 mix of Seachem's Flourite and gravel.  I am wondering if there would be any problems with my reusing this, mixed with the laterite, as the bottom layer of the new substrate.  I don't want to have
> to go out and buy entirely new gravel, but I'm willing to if this would be a bad idea.

Seachem Flourite is probably one of the most attractive substrates I have ever used. I have a 20 Gal. tank set up using Flourite as the sole substrate material and plant growth in this tank is phenomenal. Everything I have tried in this tank so far has grown extremely well. I
doubt that there is anything wrong with re-using this substrate, so long as you rinse it well to remove detritus first. But I wouldn't restrict it's use to the lower layer - Flourite is too pretty to be hidden, depending of course on your personal preference and what you have it
mixed with. There are gravels available which are close in color and size to Flourite and a mixture should be fine. As far as I know, Seachem does not add fertilizer to the material which Flourite is made of, and Greg Morin could possibly enlighten us more on this. But from the
results which I have observed in my own tanks, this calcined clay substrate material is more than capable of growing beautiful plants all by itself, without anything additional in the substrate like laterite or peat.

From the description of your proposed setup, I'd say that you have put a lot of thought into this "dream tank", and you might want to consider going with a 50-50 Flourite/gravel substrate in lieu of Duplarit G. Heck, you've already spent a bundle - go for the brass ring!

James Purchase
Toronto, Ontario