Part one; Keeping chocolate gourami alive.
Chocolate gourami have a reputation for being difficult fish to keep alive. Often they do well for a few weeks and then go into decline and die not long after. I have watched this myself on more than one occasion and wondered why.
When one reads the available literature on Sphaerichthys osphromenoides, the consensus for keeping chocolates is soft acidic water with low carbonate hardness. I have found this to be generally so, yet not really enough to keep them alive long term.
I also keep licorice gourami; the Parosphromenus. Licorice gourami are blackwater fish. They are found in peat swamps where the water is stained brown with tannins. Blackwaters are also very soft and acidic, sometimes with a pH as low as 3.
Then one day while doing some research into the native waters of the licorice, I came across one simple piece of information; chocolate gourami can be found in the same native waters as licorice gourami.
That made perfect sense; chocolate gourami are blackwater fish.
Since I keep and breed the Parosphromenus, it was simply a matter of treating chocolate gourami as I do the licorice gourami and it worked.
This is the aquarium where I keep my adult chocolates, the photo taken last night. They also spawn in there. The chocolate gourami sitting on the bottom is brooding, maybe for the eighth or ninth day now.
This 90 litre aquarium is a research project rather than a show tank. The layout design is rather simple too.
* The substrate is one or two centimetres of creek sand simply for aesthetic reasons.
* A few pieces of old hardwood branches with some Anubias growing on it provides cover for the adult gourami. Indian water sprite covers about two thirds of the surface.
* Filtration is a simple air lift sponge filter with a low flow rate.
* Heater and thermometer.
* A few Indian almond leaves
* The lights are LEDs.
* Food is live grindle worms and brine shrimp, with occasional daphnia and mosquito larvae. Frozen food is blood worms and adult brine shrimp.
The water statistics:
* pH: Normally between 4.5 and 5.5. With a target pH of about 5. The two spawnings where I remembered to measure the acidity occurred at a pH of 4.8 and 4.9.
* GH: is as low as possible.
* KH: is as low as possible.
* Temperature is set to 26/27 degrees Celsius.
* A 20% water change per week.
Blackwaters are typically very soft, very acid, with very few nutrients and high in tannins, humic acids and fulmic acids which stain the water brown.
To achieve the very soft water I use reverse osmosis water.
To achieve the acidity I use a product by the Seachem company called "acid buffer". Acid buffer also changes carbonates (KH) into carbon dioxide. The water is prepared a week in advance to age it. Stored in fifteen litre containers, treated with a de-chlorinator, the pH dropped to between 4 and 4.5 and aerated until required. In the containers the pH is stable.
In the living aquarium, the pH naturally rises over the course of time. Within a week or two the pH can rise from 5 to 6. This is probably due to the micro-organisms. Biological activity using some sulphur in the water (sulphuric acid in the acid buffer) to combine with phosphorus, nitrogen and so on from fish pee and poop. I am not a chemist but can understand some basics.
The question of removing nitrates, phosphates and so on that build up in the aquarium is achieved partly by the 20% weekly water change, and partly by the use of the floating layer of Indian water sprite which is quick growing and acts as a nutrient sink. Regular cleaning of the aquarium floor is also necessary. A low stocking rate helps here.
When you have a pH below 6, the idea of nitrogen fixing bacteria and conventional biological filtration doesn't really work all that well. The nitrogen fixing bacteria like a pH above 6 according to the research I have read.
So one cannot conventionally "cycle" a blackwater aquarium due to the acidity and softness of the water. My strategy is to put the aquarium together, inoculate it with a glass of water from an old aquarium and then let it age. After a few weeks one starts to see cyclops and other tiny water creatures on the glass, algae begins to grow. The "empty" aquarium is alive in its own right.
The tannins and humic acids are achieved as the wood and the Indian almond leaves break down. I don't use peat at all, mainly because I don't know where it was mined and what it contains.
An important point to remember is that in very soft and acidic water, many pathogens and other bacteria don't grow well at all. Firstly because the pH is outside their liking and secondly; in nutrient poor water the building blocks of life are in short supply. Bacteria need nitrogen, phosphorus, potassium and so on to create the building blocks of life. I think this is one of the important keys to keeping chocolates; biologically clean water. Chocolates probably don't have a strong immune system to begin with. Perhaps simply because they didn't need to evolve one in their very clean native waters.
Next is spawning, brooding and caring for the fry.
Edited by Albert, 03 October 2020 - 08:29 AM.