Okay so you guys talk about BIG water changes and I have also heard people tell me to do small 10% water changes. Previously I was doing 25% water changes once a week. So I’m not sure what the right thing to do is. My concern is that with doing such large water changes you are drastically changing the balance of the water every time you do it.
A water change of 10%
every day is next to useless. You simply cannot remove enough of the "crud" to help. There was an article in TFH a couple years back with math showing why one 70% WC each week was way more beneficial and effective than 10% changes every day. Colin has written about this too. All I will say here is that you can never change too much water, as far as the fish and plants are concerned; with the plants however, you do need to make sure nutrients are available.
As I tried to explain previously, my tanks have such a stable balance because of the large changes. My GH and KH are zero out of the tap and I add nothing (I have all soft water mainly wild caught fish). I do use substrate tabs primarily for the "hard" minerals, and these plus the comprehensive liquid have been sufficient for the plants. I did use Equilibrium for some two years, to raise GH for the plants, and it certainly was effective, but fish issues I won't get into caused me to re-think this, and the substrate tabs have now, after some three years without E and just the tabs and liquid, proven to be sufficient. But it depends upon the plant species, light intensity, and CO2 [I'll come back to this below]. But my tanks are extremely stable with respect to water chemistry. Some of them have a pH below 5, some around 6, and this has never changed in years. Tap water is pH 7 but this is due to the soda ash they add to raise it as it is naturally below 5. The change in the tanks with such large WC's has shown to be around 0.2 or 0.3 which then lowers back by the next day. That is stable water.
Now, if you have tanks with low GH/KH/pH, and you do massive WC's with much harder water, this is a problem. But assuming you use the source water and have fish suited, there can be no issue with large water changes. Discus breeders regularly change 90-95% of their fry tanks' water two or three times each day.
The gravel or sand substrate that you use instead of soil, does it contain nutrients for the plants as well or is it only a medium for the plants to grow in? I had a volcanic rock type substrate. I use to put fertilizers but found I had a chronic problem with nitrates about 100ppm.
My substrates are inert; plain play sand or sometimes regular fine aquarium gravel if I want an aquascape replicating a S Asian river for loaches, or if I were to do a Central American river for livebearers. The tabs are the only plant additives in the substrate, and only for the larger swords. I did try
Flourite plant substrate once, on the advice of members on another forum, but in the end I tore the tank down after two years and dumped the expensive
Flourite in the garden. The plants were no better to my eyes, and the roughness meant I had to remove my cories when they developed barbel loss and one even lost a bit of its mouth [all recovered over play sand and I still have them, some six years later]. Not worth it.
Sand is overall better as a plant root medium, and for many fish.
I just never seemed to be able to have a happy tank with happy plants and fish at the same time when I was doing 25% changes weekly. I think I was over feeding for a long time which was also an issue. I had carbon in my filter which I think was a mistake as well as it was filtering out a lot of beneficial things
Yes, carbon may be detrimental, it will remove some nutrients. Filtration is actually not good for plants, but they can manage provided it is not extreme. The balance (light intensity and nutrients) is key with plants, and every species is different so mixing this and that frequently results in failure because the plants are being forced to adapt. I start out with the light...I know the detrimental effects of bright lighting on most forest fish, so I have low to moderate, no brighter. Then there is spectrum...plants need red and blue to drive photosynthesis, and adding green to this mix does improve plant growth. Probably because this is close to mid day sun, around 500K to 6000K. The "daylight" tubes/bulbs with 6500K are just about ideal, according to scientific studies. I use a mix of 5000K and 6500K when I have two tubes over a tank.
Once the light is set, then you find plant species that are suited, and you provide nutrients to balance. If you noticed in my photos earlier, there are swords, crypts, Java Fern, Java Moss, Anubias. That is what grows under the lighting intensity I provide. And I have floating plants which I view as mandatory for all fish, so the light is even less strong. These plants grow like weeds. I have tried other plants, they usually fail and melt within weeks, so I move on, until I have the plants that work.
