When I decided to make a pond at my backyard, I wasn't planning to keep koi in it. My plan was to make a pond water plants. If I knew what I know then, I would have my pond setup at a different spot at my yard. Hey my pond is still worked out fine, only I have koi in my pond now instead of original plan to keep water plants.
The pond that I have is a 125 gallons pre-formed pond. Basically a molded black color rubber tub in kidney shape. The measurement is 6ft x 4 ft x 18 inches deep.
Here's what I did,
1) Shading, the single most important thing for a small fish pond. I build a canopy with 1" PVC pipe and a corrugated vinyl sheet. Total materials cost me about $25 Canadian (approx. US $18). It block lots of direct sunlight during the day time. The sun warm up the temperature of the water during the day time to 29 degree C, and it cool down to 14 degree c at night time. The temperature fluctuation stress the fish so bad.
I had tried different things before I build the canopy. I bought some artificial lily pad and float them on the surface. It gave some shade to the fish but not enough and it does not help temperature problem. Finally, canopy idea vame in my mind, it successfully reduce the water temperature fluctuation.
I also bought a Rena Air pump for the pond. I tried to install a split on the hose, thinking that I can get air on the pond and also for the filter chamber. Well the pump isn't powerful enough to handle the split. I tried both locations and want to see if there is any noticeable difference, ends up the air stone is in the pond.
2) Change water & vacuum.
Step One - Change about 5% of the water everyday (drain the dirty water out from the bottom of the filter chamber). The filter that I have is mechanical & biological filter in one chamber. I have a bottom drain at the bottom with a value to operate. Drain out the dirty water here and I used the dirty water to water my flower.
Step Two - Vacuum the pond bottom with a homemade vacuum cleaner. Basically it's a leftover piece of 1/2" PVC pipe that is being connected to a section of leftover hose, and then connected to a rubber squeezing thingy. I use this vacuum to suck out about 10 gallons of debris & dirty water from the bottom of my pond.
Step Three - add water back to the 'full line' and of course de-chlorine the tap water.
I did Step 1~3 for 5 days. For the first two days, not much improvement. On the fifth day, the water is much less green already.
Start from Day Six, I change about 5% of the water. I did it for another week (again drain the water out from the filter chamber). I didn't need to vacuum the pond bottom anymore becuase I find that its quite clean now, visually. By the end of the second week, the water clearing up so fast that I can't believe my eyes.
The whole water quality improvement process cost me $25, and it took me an afternoon to build the canopy. It took about two weeks for the good bacterias to grow. Now my pond water is truely crystal clear. I can see even a tiny piece of fish s**t at the bottom. I don't need to change the water anymore, however I do need to add water to cover the water lost due to evaporation.
I still vacuum my pond once a week because I don't have a bottom drain in my pre-formed pond.
My water condition now is:
pH 7.2
Nitrite 0.05
Ammonia 0.0
temperature 22~25 degree C
No more sick koi.
What I have learnt: patience is the name of the game.
I had pea soup problem, temperature problem, and crazy high pH problem before; now water is all clear up, temperature steady and pH stays at 7.2. It cost me very little money to fix the problem.
