My parents have been having problems with their pond I mean the pea green color,not the usual blanket algae. Even the water hyacinths weren't looking good, well yesterday all their fish were dead, I told them last week when I was over the fish were suffering from lack of o2 they put in another filter fountain. Anyone have any ideas on this? and what they can do to prevent this. Some of those fish were at least 10 yrs old.
I would guess, based on there being a good history of healthy pond water, that there was a build up of fertilizer in there. Nitrogen in the form of run off or overspray from the yard or too much fish poop in the water can cause a nutrient overload, algae bloom, and when the algae dies off the oxygen is consumed by the bacteria breaking down the dead material. Generally, the problem takes care of itself but it may be the only way to fix this one is to drain the pond and start over. Be warned that new water will likely have an algae bloom in the first few months, but it generally clears on its own and is good after that. You mention filter fountain, but do they have an external filter with something where bacteria can grow for a bio filter? For a pond of a certain size (maybe 500 gallons?) and certainly one with fish this is necessary to get rid of the excess nutrients. That prevents the algae bloom and to some extent the blanket algae as well (though that stuff grow almost anywhere!).
Are you talking big farm pond? If so we have been advised that we need a bottom aerator. The fountains on top of the water don't do a good job of getting O2 to the bottom of the water where it is really needed to allow bacteria to eat excess nutrients. Also if the water 'flips' (not quite the technical term) you have the fish kill from the un-oxgenated water coming to the top. Try looking up the 'pond guy' or 'pond doctor' online.
First, is this an ornamental small pond or a big 'real' pond; and second, have there been any other changes e.g. adding grass carp to a 'real' pond or alterations to the plants or water source of a little ornamental pond. Basically the reason for the pea-soup water (which is doubtless what killed the fish - lack of O2 at night, and/or lack of O2 from the pea-soup algae starting to die and decompose; also pathogens can be more numerous in such water) is Too Much Nutrients in the water. "Too Much Nutrients syndrome" results from some combination of too much goin' into the pond (in the form of high-nutrient-load water, fertilizer, fertilizer runoff, too much fishfood, ducks pooing in pond, manure runoff into pond, etc) and too little bein' taken out (by floating plants, by submerged plants, by the fur-like algae that grow attached to submerged surfaces, and binding in well-oxygenated sediments). Without knowing the precise chain of events that caused your parents' pond's problem, the generic and usually useful solution is as follows: 1) Starve. Eliminate all possible routes by which too much nutrients may be entering the water - this includes feed your fish smaller amounts and probably less often, keep poo and fertilizer WELL away from the pond, check the N and P content of water used to fill the pond, etc. 2) Stir. Encourage phosphorus to get bound into the sediments by ensuring the whole pond remains well-oxygenated at all times -- this will probably require mechanical circulation such as a little fountain. (They are NOT just for looks, and however stupid you may think they look, they perform an important role, and even farm ponds sometimes require them for practical reasons). This will prevent the pond from stratifying into a hot upper layer that remains isolated from a cooler lower layer, the cooler layer becoming anoxic because the hot layer sittin' on it shuts it off from atmospheric oxygen. 3) Suck (the extra nutrients into plants, that is). If this is a small ornamental pond, you can often get good deals on floating plants like water lettuce or water hyacinth this time of year (I recommend this only if your parents are in Iowa too, not somewhere like Florida where those plants are banned as an environmental menace ). Get a lot of them, and some submerged waterweeds as well (again, avoid things that become an escaped problem in your region). They should grow like gangbusters - keep them well-thinned enough that they are always growing at their maximum rate. You can pull out any extras and chuck 'em on the compost pile. Also -- this is really really important -- pull out any that look like they are degenerating or dying, including probably ALL of them at the end of the growing season when they start to turn brown or yellow - the whole point is to permanently REMOVE FROM THE POND the nutrients that gets put into their growth. You REALLY do not want them decomposing back into soluble nutrients If it's a small ornamental pond, it would be worth suction-vacuuming out all the muck and dead organic matter that has settled to the bottom, and if practical you can also do a partial water change (how 'partial' depends on what the new water would be like, and on whether you have any fish left you're trying to save). You should also inspect whatever filtration system you have, and make sure there aren't giant goobers of organic crud sittin' there releasing nutrients. If it's a farm pond, getting rid of grass carp if possible will help, and if the banks are getting overgrown with bushes and trees it will also be helpful to cut that back (at least on the upwind sides) so that mroe breeze goes across the water -- this helps keep the water stirred and unstratified (thus more oxygenated). Good luck, Pat
