Probably. There are "guidelines" that are designed to give you an idea of the ratio of koi/goldfish to number of gallons. Here is a link for a "fish calculator," that gives you roughly how many fish-inches for number of gallons. [Scroll down a tad and it also gives a link to a "pond volume calculator" so you can plug in your pond's measurements to see how many gallons it is]
http://www.your-garden-ponds-center.com/fish-load-calculator.html
There is also a "rule of thumb" about 1000 gallons for the first koi, then add so many gallons per koi thereafter. Keep in mind that fish grow [and multiply], so your pond is always in a state of flux.
This is what I think your problem is.....[and I'm NOT an expert]. I think you have too many fish and your filtration system [mechancical AND biological] is having a hard time keeping up. So, more than just not being able to
SEE your fish, they could be under stresses that could eventually lead to serious illness.
"Unclear water" is a symptom (but isn't necessarily a bad thing), but the first step you need to take is to
figure out WHY your water isn't clear in the first place!. To fix the
symptom that the water isn't clear, you have to fix
any underlying issues. In this hobby you will find an unlimited supply of opinions on how to take care of a pond -- many are not right or wrong.....just different. Keep in mind that every pond is different, to what works for one person or a hundred people, might NOT work for your particular situation.
This is my suggestion:
- Get a liquid test kit [API is what I use]. These can be found at most pet stores or you can order them online. Strips tend to not be as reliable.
- Test your water parameters [and keep a record of them, along with any interventions]: ammonia, nitrite, nitrate, pH, KH, GH.....
- Learn as much as you can about the nitrogen cycle http://www.michigankoi.com/Understanding-the-Nitrogen-Cycle-Koi-Pond-Water-Information-sc-280.html -- this is something every ponder needs to know, but in your case it will be helpful if you end up having to start over with a clean pond, clean filters, and fresh water. Your pond will have to go through the "cycling" process, which takes weeks.
- Rehome as many of your fish as possible!!!!! Smaller ponds can only handle a couple of koi, however, you might want to consider goldfish as an option.
- If possible, set up a temporary pond to hold your fish while you do the next few steps. I won't go into it here, but ask and we can help you through that process.
- Find a pool skimmer net [or something similar] and scoop as much of the crud as you can from the bottom of the pond.
- Pond vacs ARE great if you don't have a bottom drain. I have an Oase Pondovac that works great -- there is a major learning curve with it, so don't give up if it doesn't seem to work at first. BUT, do step #6 first. I didn't mention this when you first posted because I wanted to see the overall picture of what you were dealing with.
- If your water is treated in any way, you'll need to add a product to remove the chlorine and chloramines -- check with your water company to find what they treat with. Most folks with well water don't have to treat their water, but it is a good idea to test your "source" water [city or well] to check for pH, KH, and GH. This is your baseline!
- Clean your filters -- if you can clean them pond water, you can retain some of the biofilm that is your beneficial bacteria, but it that's not possible, refer to step #3.
- Sometimes you have to reasess your filtration system -- something else we can help you with later -- but right now let's get you started with testing your water, reducing your fish load [no, it's NEVER an easy step -- but short of building a larger pond.....] and netting the gunk from the bottom of the pond [worry about the vacuum later -- it's a luxury item, not a necessity]
Hope this isn't too long-winded, but most of all, hope it helps!