Plant growth substrate

In a 240 l tank, I'm building a paludarium, thus reducing the water volume to about (probably less than) 100 l.

Two HO 6500 K fluorescent tubes, no CO2. Tap water is rich in NO3 (40 mg/l), and pretty hard (total hardness 13 dH).

Am I right that all plant growth substrates contain peat, and therefore lower pH? I'm quite worried about this, since, with such a small water volume, and hard water, every time I'll do a water change the pH may change abruptly??

Or am I totally off, and I simply shouldn't worry??

Thanks!

By "plant growth substrates," I will assume you are referring to aquarium plant substrates, not terrestrial plant substances. Some of these might contain peat, but many do not. Some will actually raise GH/KH/pH if they contain minerals.

Aside from the above, though...the pH is tied to the GH and KH. The KH especially will serve to buffer the pH, preventing fluctuations. Consequently, even using peat might have no effect. This depends upon the initial GH and KH of the source water, as well as the amount of peat or other organic matter; all organic matter will naturally acidify the water and lower the pH, but again this depends upon the intial buffering capability. A GH of 13 d is fairly hard (to use a subjective term), and I would expect the KH to be close. If this is the case, then the pH is not likely to lower much, if at all.

Byron.

If you are talking about products like Caribsea eco-complete substrate, I say don't waste you money on it.
I had this stuff in my tank for over 6 months and did not notice ant difference to plant growth, Also it is too sharp for things like plecos loaches and corys.

Thanks!
Yep, forgot to mention the KH, which is at 9 dH. So, I guess I do have some buffer.
Yet, to play safe, can you recommend any substrate which does not contain peat?

I just checked the latest measurements from the municipality. Surprising how low the pH was recently (7,2).

Cheers

Maurizio

I confined my previous post to responding directly to your question. But Nick has raised a pertinent point, so it might help if we knew a bit more about the intended paludarium.

Picking up on Nick's post, many of these so-called plant substrates are of little or no benefit. Then one has to consider the possible tampering with water parameters and conditions that they can bring. If fish or aquatic creatures that respirate aquatically are intended in the aquatic area, this is a very crucial aspect. The materials are often rough, which can be very harmful to substrate fish, as I learned first hand.

Most aquatic plants take up nutrients via roots and leaves (some are exclusively or primarily via the leaves), and substrate nutrients may have little benefit, depending upon the plant species. There are the substrate fertilizer tabs, like Seachem's Flourish Tabs (I use these) that supply excellent nutrients to larger substrate-rooted plants.

I have had planted tanks for over 20 years, and my substrates have been fine gravel or (now) play sand. I did experiment with a plant substrate once, Seachem's Flourite as it happens (which is nearly identical to CarribSea's Eco-Complete that Nick mentioned), and it was useless. I tore it up after two years of fish problems and basic plant growth, and replaced it with play sand. There is a lot to the balance between light and nutrients, and the substrate is probably the least important factor in this, provided it is of a particle size that promotes plant growth. Anything from sand up to pea gravel, but no larger, can work well, with some conditions. I have found sand better than pea gravel, due to the particle size.

Byron.

Thanks a lot Byron.
As usual, it's more complicated than it seems at first.

Well, my previous (and only) experience with aquaria (you can see the details below) used plain sand, and fertilizer tablets (Tetra Crypto), same lights mentioned above, and no CO2. Pretty bad results, but surely brackish water doesn't help... So I promised to myself to use a growth substrate in my next experience (now).

My plan is to use Dennerle Crystal Quarz gravel Diamond black - size 1-2 mm, reportedly safe for bottom dwellers (I'm not planning any, but let's play safe) - as a topping, and a substrate for better plant growth. I'll happily skip on the latter, if you say I can live with just tablets!!

Well, my previous (and only) experience with aquaria (you can see the details below) used plain sand, and fertilizer tablets (Tetra Crypto), same lights mentioned above, and no CO2. Pretty bad results, but surely brackish water doesn't help... So I promised to myself to use a growth substrate in my next experience (now).

I would suggest the issue here was too much light. T5 HO tubes are very intense lighting, and without CO2 and regular (daily) fertilizing, this would not likely work. It could, but it takes a lot of effort; floating plants can help, and less duration. Brackish water could also factor in, depending upon plant species. Salt literally dehydrates plant leaves, same as leaving them in the air, and while some plants can manage, others cannot. We can leave this, but just thought I'd mention the likely issues.

My plan is to use Dennerle Crystal Quarz gravel Diamond black - size 1-2 mm, reportedly safe for bottom dwellers (I'm not planning any, but let's play safe) - as a topping, and a substrate for better plant growth. I'll happily skip on the latter, if you say I can live with just tablets!!

First, on mixing substrates. This can work, but make sure you plant all the substrate-rooted plants in the first "enriched" layer before adding the top fine gravel layer, otherwise you will mix them. They may mix naturally with time, depending upon the substances themselves. Water is (or should be) continually moving through a healthy substrate. The water in the substrate is warmed by the bacterial decomposition, and it rises back up into the aquarium while the cooler water will percolate down. This can often mix substrate materials and move them about, more than one might think.

As for the benefit of the enriched bottom layer, this depends upon the substance and the plant species. If you want a carpet layer (say dwarf hairgrass or clover-types) covering the substrate, then an enriched first layer might benefit. But you can always add liquid nutrients which will, because of the water flow through the substrate I mentioned above, get down to the plant roots. But many plants will do just as well without this. You are intending CO2 and you have intense lighting, so nutrient supplementation will be essential in some form. I've never gone down this road, as I have no need to, since I maintain fish with plants being secondary and provided they thrive I'm happy. I stay with those that do.

I'll add a photo of my present 70g and 90g tanks just so you can compare; these are natural or low-tech systems, no CO2, some liquid fertilization, substrate tabs next to the larger swords and lotus, and moderate lighting which is two 48-inch T8 tubes, one 6500K and one 5000K over each tank. The plants are growing like weeds.

I just spotted something in post #1 I haven't commented on yet. Nitrates at 40 ppm (mg/l = ppm) is high for fish. Nitrates should be kept below 20 ppm. Your plants may use some of this, but not all. Might be worth looking into. Enriched plant substrates may contain nitrates too, depending what they are composed of.

Some of our members have experience with nitrate-high source water and will be able to offer suggestions. B.

Byron,
thanks a lot for the good advise, and the time it must have taken to write all of it. And a big WOW for your tanks, I can't believe that stuff is low-tech!!! They're a beauty!

To complete the picture, the tank depth is 50 cm, and water depth will be only 20 cm, so a pretty short travel for light. But hopefully a lot of shade from the aerial plants. The reason I'm aiming at 2x90cm 39W HO lights (plus reflectors) is that most of the aerial walls of the paludarium will be covered with moss, which reportedly requires quite a lot of light (I'm told 7000 lm, which those fluorescent can't really reach...).

As for plants, I'm aiming at the easiest I can get. Surely some floating (Phyllantus Fluitans, if I find it). No carpet layer. No CO2 planned at all. I can surely do without enriched bottom, if liquid fertilizer can substitute it.

Is all this feasible?

NO3: yeah, old issue. The whole country is soaked in it. The exact value oscillates around 36 mg/l. That's the main reason for me to heavily plant. Originally I hoped to cycle the water through the walls, to have the aerial plants use it, but practically all of them require pure rainwater, so no chance: I'll have to rely solely on the aquatic plants. As a beginner, I tried all I could with the previous tank (spent a couple of years fighting and researching the matter, but excluding high-tech solutions such as RO, ethically unacceptable for me, or collecting rain water: my dream of a marine tank ended with this). Another thing is, it will be raining pure water a number of times a day, in there, so this may help diluting the nitrates. Maybe. And advise is most welcome...

To complete the picture, the tank depth is 50 cm, and water depth will be only 20 cm, so a pretty short travel for light. But hopefully a lot of shade from the aerial plants. The reason I'm aiming at 2x90cm 39W HO lights (plus reflectors) is that most of the aerial walls of the paludarium will be covered with moss, which reportedly requires quite a lot of light (I'm told 7000 lm, which those fluorescent can't really reach...).

You will obviously have light dispersal through the air before it reaches the water, and this will lessen the intensity to some degree. Plus the aerial plants. May well work out fine. My 90g is 60cm depth, the 70g is 50cm.

Mosses generally are lower light requiring, but there may be some you are intending that need more. I won't counter this as I've no direct experience.

As for plants, I'm aiming at the easiest I can get. Surely some floating (Phyllantus Fluitans, if I find it). No carpet layer. No CO2 planned at all. I can surely do without enriched bottom, if liquid fertilizer can substitute it.

Sorry, I misread post #1, you did say "no" CO2. That being the case, I would forget the enriched substrate. A single material substrate is always easier to manage. Also makes life easier for aquatic critters, fish or whatever is planned.

NO3: yeah, old issue. The whole country is soaked in it. The exact value oscillates around 36 mg/l. That's the main reason for me to heavily plant. Originally I hoped to cycle the water through the walls, to have the aerial plants use it, but practically all of them require pure rainwater, so no chance: I'll have to rely solely on the aquatic plants. As a beginner, I tried all I could with the previous tank (spent a couple of years fighting and researching the matter, but excluding high-tech solutions such as RO, ethically unacceptable for me, or collecting rain water: my dream of a marine tank ended with this). Another thing is, it will be raining pure water a number of times a day, in there, so this may help diluting the nitrates. Maybe. And advise is most welcome...

I would suggest that the plants are not going to make much of a dent in nitrates this high. Remember too that nitrates will occur naturally in the water portion, depending upon fish levels. My tap water is zero and the tanks run in the 0-5 ppm range, but this is primarily due to my massive water changes; I change 50-60% every week. There is very little nitrate in the Flourish fertilizers I use, and they are dosed at less than recommended level, so not much is entering the system.

Nitrates above 20 ppm long term are now believed to have issues for fish. As I said, other members have dealt with this, Abbeysdad (Michael) comes to mind, so if he doesn't see this thread and comment, you might want to send him a PM and he can offer the benefit of his experience dealing with nitrates in the source water.

Byron.

Lots of thanks, Byron, will PM Michael.