What kinda medication are you using ?
IME many meds do not catch it first time around. The quality of the meds and the dose has alot to do also. I am NOT one to use Meds UNLESS it means Life Or death. ich is one of those cases.
I use Maracide by Mardel Labs. I have used it for years and ALWAYS get rid of the ick within the treatment time.
Most times before treatment is scheduled to end. This Medication will tinge the tank a slight greenish color but is removed once treatment is over with some freash carbon and a water change.
This meds cures a wide variety of external parasites and I highly reccomend it. I have used and still got several other brands / kinds of ich meds that I personaly didn't find as affective.
I have used and some times use Quick Cure but again it's NOT as affective with the ich.
Now you know ick can and will rermain dormant even if there are no sighs of infections. If you are medicating the tank and stop or meds were not powerfull enough it MAY appear the ich is gone but it can be dormant and return normally is higher numbers and a worse out break.
Me, all I do is treat as needed: 1 drop per gallon every 24 hrs for 5 days. And normally within 3-4 it's done and gone. I do a good 30-40 % water change, add freash carbon and within hours walla. Good as new.
I use salt during water changes so I never really add some more nor do I even add when treating for ich. In the cooloer months I will run the heaters to assure the temp does NOT drop to fast nor get too cold. This is most times the main cause for an ich outbreak.
I personally have problemns if any during the winter months. Cold water fish are affected or stand a better chance of getting ich when temps get warm. And vise a versa for warm water fish ( most cichlids ) are affected when temps get to cold. Secondary inffections, bad tank maint., can also and will make the odds of ich higher.
What is ich ? Ready ? hehehehehe
Ichthyophthirius multifiliis
Means " fish louse with many children" It was named as so because one parasite can produce as many as 600 - 1,200 youngsters.
The parasite penetrates the mucous coat here the growth process begins. The parasite feeds on red blood corpuscles and degenerated epithelial cells.
When after some days in the fishs skin the parasite matures. Now it's time to leave the host (fish) for reproduction. The mature parasites having left the host, sinks to the bottom and starts to go through even more changes, here it secretes a soft, jelly like cyst.
Here is where the water temp makes a diff on the time it takes to develope and time / extent of infection accours.
The speed of this process depends on the temperature of the water: normaly about 12 - 18 hours. Approx. 36 hours after the mature parasite has left the host, the youngsters will be swimming in a lively manner in search of a host.
Now the parasite has already entered the fish, ate, left to reproduce and the young are now in search of food a host ( your fish )
Thus, in the aquarium the parasite leaves the fish (s) periodiclly, but the fishes are infected again and again and everytime evn worse.
Developement of ich in the aquarium takes diff times, depending again on the temp of the water.
From 78-80 *F the parasite will leave the fish 3-4 days AFTER the spots were viss. to to naked eye. At temps lower than 70* this period can take up to 4 WEEKS or more. Thus, increasing the temp will decrease the time that the parasite remains in / on the fish. But, it ALSO shortens the time before reinfection occurs.
Raising the temp should ALWAYS be combined with some form of medication ( Maracide IMO ) HEAT ALONE WILL NOT KILL THEm. oops sorry cap lock.
The young parasite can not life long without a host and die within a few days if non is present. At longest a free swimming parasite can / or will not survive longer than 55 hours without a host. YOUNG parasite that is, still got the mature ones to tend to . Meds and raising the temp.
As I mentioned prior, most cases of ich occur in autum and winter, If a completely healthy fish is infected by one or two parasites it will not suffer muchy, and if the tank is NOT crowded the chances of reinfection are NOT to great.
In such cases, infection may remain in a latent stage for a long period,since the parasites in the skin of the fish it will grow very slowly and consequently no symptoms of ich will appear.
However, if the resistance of the fish is weakend by unsuitable conditions the parasite will have a better chance and THEN the epidemic may accur.
This explains why epidemics often appear when tropicals are kept at too low temps., while on the contrary, in cold water fish epidemics may accur at too high temps.
Now here is the kicker,
Cysts of ich can often be found on water plants, which explains and is how most time these parasites are smuggled from tank to tank. Ever bought a fish that appeared healthy and when you get it home and put it in your tank walla. ICH. As I mentioned above there are a few factors that can and will contribute to ich and also how long in lingers around.
There, Hope this helps and Hope you enjoy my Mini Book. LOLOLOL You Guys were warned....
Increase aireation, Do a partial water change to eliminate previously used meds, get some GOOD affective Meds ( Maracide), cut back on feedings till problem is under control. I am surprised a bit though because plecos are normally the last ones to get / show signs of ich. Must be a pretty tough outbreak.
Danny