Terrible Advice Tuesdays: What REALLY Kills Ich (Cryptocaryon irritants)

Terrible Advice Tuesdays: High temps kill ich. (Suggested in the context of cranking up a tank’s temp to kill the disease)

The rest of the story: To some extend, this advice is true. If you get your tank hot enough, ich will die. Never mind the fact that to get your tank that hot, your fish and coral will very, very likely be dead long before you reach that point! Note: I could not find a specific temperature at which ich has been scientifically proven to die. I’m confident that it is above the ~90F (32C) temperature that most saltwater fish in your tank will tolerate.

Part of a proven ich treatment plan is to elevate the hospital/quarantine tank’s temperature to 80F (27C) to speed the disease through its lifecycle. All that you are doing is speeding up the lifecycle of the disease though. Without proper treatment, the disease will continue to live and thrive.

Tolerable elevated temps help a proper ich treatment plan, but simply cranking up your tank’s temperature in hopes of killing the disease will keeping your fish and corals alive won’t work.

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Comments for this article (23)

  • Damian Williams says:

    Hi firstly would like to say I’m a big fan and your videos have helped me over the last 2 years of my saltwater tank. My tank is 6ft by 2ft by 2ft in 2 years I’ve never done a water change and use carbon dosing and skimming to keep nutrients low. I took my eye of the ball a few months back and stopped dosing vodka and skimmer also was having issues leading to water quality issues. I noticed ich on one of my fish at which point I started trying to find a cure and started dosing which drop nutrients within a few days Before I knew it most of my fish where showing signs of ich and I started losing fish very fast. I didn’t have the space for a quarantine tank and im sure trying to catch them all would have done more harm than good. I tried garlic I tried ginger with no avail. I them came across the temperature theory. The raising of temp apparently causes the ich to form a cyst and stay dorment for some months. But as far as I knew ich has always been in my tank and it was my water quality that lowered my fishes immune system allowing the ich to take hold. Increasing temp allowed my fish to recover and build there immune system up before dropping the temp a few months down the line. In theory putting me back to where I was before ich was noticable. Haven’t lost a fish since temp increase and have no signs of ich on any of my fish.

  • Joe says:

    So it sounds like Damian still has ICH.

    Outta sight outta mind?

  • Shawn says:

    I’m convinced our hobby doesn’t know what it thinks it knows about ich. Years ago I had a brand new large aquarium that I’d introduced one fish into, which immediately ich’d out. I caught him and put him in a hospital tank, where I treated him with copper, kept temperatures elevated and endured he got really good nutrition. His ich quickly disappeared but I continued dosing as recommended and kept him in the hospital tank for over six weeks. According to all the literature this should have been enough to kill his ich problem off, as well as allowing the ich in my main tank to die off with no other fish in that tank. At the end of the quarantine I used brand new nets etc. to collect the fish and move him back to the main tank. The very next day he had ich again.

    I think that kind of like human hospitals, there are tons of pathogens on the loose and while there are general statistical guidelines for everything there’s no guarantee that a particular instance of a pathogen is going to operate that way. I think some strains of ich maybe really could be innahillated by increasing temperature, while others might persist through just about anything.

  • JasPR says:

    many of these home remedy treatments ( which is what the marine hobby has used since I entered it in 1970) are simple an example of –” if you add or raise it to here, the parasite is under stress, if you raise it a little more, the fish and the parasite are under stress and if you raise or add it even more– the parasite, the fish and now the hobbyist are in stress!!”
    we are only left then with chemotherapy ( another poor remedy but the only one we have) and antibiotics ( mixed reviews). This is why I begin with injects for disease anyway, in the 1990s.Far more controlled and effective. JasPR

  • Lori says:


    I have a 55 gallon saltwater tank. I have had tanks for over 40 years now.
    I too, have dealt with the ich problem and have lost beautiful fish. I now for over a year have found a solution..in my opinion…that has given me hope of,
    hopefully never having to deal with this problem again.

    I use Dr. G’s anti parasitic caviar in my tank about twice a week. Once a week I use just regular Dr. G’s caviar. My fish love this stuff and I am treating them for ich from their food source and not the water itself. I have had great luck with this and wouldn’t stop using it for anything. It’s pricy about $25 for a 8oz bottle but it last a long time and is well worth the money to keep my beauties alive and healthy.

  • Damian…part of ich’s natural life cycle is to form a cyst and raising your tank’s temperature only sped up the lifecycle of the parasite. The elevated temp encourages a faster cystic stage. It doesn’t prolong that stage. What likely happened was that the elevated temps caused any ich to fall off the fish (again part of the natural life cycle) and encyst. Your fish may have built some resistance to the disease during this time which is why you haven’t seen it on a fish again. Keep in mind that there is scientific evidence of fish carrying ich, but not showing any signs of the disease. Therefore, ich is still in your tank, you just aren’t seeing it.

  • Damian Williams says:

    Some research suggest that at 90 degrees ich defenses make them speed up yes but they wont release there young from the cyst while at that temperature. The cyst can stay dormant for many months. Now I probably had ich from the first fish I introduced and this wasn’t a problem to me or my tank untill ich took control and started harming my fish. I know ich is still in there and to remove all fish from the tank for 6 months isn’t a option well not till I decide to get a bigger tank anyway…..(shhhh don’t tell the mrs) it was my lack of dosing that caused the stress which in turn caused the outbreak otherwise I may have never know I had ich. Within 4 days of raising temp all spots had gone. I left temp for 4 months before lowering it again. Another 3 months have passed since then and all survivers are looking very health and stress free. It may not be the best option but I’m alot happier than I was.

  • Kyle O says:

    Damian………you have never done a water change in two years???

    ICH is very tricky and there are a lot of different opinions. I have been at this for a little over 10 years now, and I see ICH infestations kind of like viruses going around (even though it is a parasite). What I mean is that viruses are always present, but some people come down with a cold and some don’t, although pretty much everybody is exposed. The people that are most prone are the ones with compromised immune systems (stress, poor diet, bad environment, etc)

    My thinking is that if you can keep your environment as pristine as possible and make sure all inhabitants are getting their nutritional needs meet through a varied diet……the chance of a system-wide outbreak is at a minimum.

    Since my Powder Brown Tang is the most sensitive fish in the tank, I keep an eye on him. Every once is a while I will see the hint of a few white spots (cysts). I start looking for an issue and clear it up immediately. Within a few days, he is clear. Of course I am watching all inhabitants closely for the next week or so.

    I even had an incident where I introduced a Solar Wrasse without quarantining, and within one day the Wrasse had noticeable cysts. At that point I was convinced I just crashed my tank and Mark’s words were ringing in my ears.

    Withing days of him adjusting, all cysts were gone and no other fish showed any signs. That was almost a year ago.

    I don’t think ICH is eradicated from our tanks………ever. I just think it is a matter of immune systems being as high as possible.

  • Joe says:

    I think ich can be eradicated.

    Quarantine your fish.

    Keep your tank fsllow as long as it needs to have the ich die.

    Keep fish quarantined snd healthy.

    No substrate in your quarantine snd water changes in your quarantine.

    Quarantine new fish minimum 2 months.

    No more ich. A parasite doest live dormant in a fish waiting for a trigger…

    Thats why its called a parasite and not a virus.

  • Joe says:

    It just seems one of the commenters is as lazy as they come with husbandry, which is why he’s always battling ich…

  • KyleO says:

    Joe, I don’t think you were referring to me as far as being lazy and always battling ICH, but I wanted to clarify a point from my previous posted (and my view point).

    I have never had to perform any type of treatment for ICH. No medication…….ever. No removal of fish to keep the tank fallow for any length of time. I do think that Quarantining is mandatory (even though there have been times I didn’t adhere to it).

    I keep a close eye on the environment and keep any type of stress to a minimum (along with a varied diet).

    One of the first comments I almost always hear when I am fragging and having a people show up to pick up their frags……..is how amazing all of my fish look.

  • Damian…I’d be interested to read the paper on how ich won’t release their young at 90 degrees. I didn’t run across it during my research for the QT guide and if there is some information I missed, I want to make sure I get that info

  • Robert says:

    So I have heard that hippo tangs are pron to getting ick. When I first got a hippo he was small got ick and died I then waited a few months other fish were fine and added a larger hippo. He has been in there for a month no ick and no issues. So does this mean ick is still dorment in my tank?

  • Robert says:

    Sorry ich not ick.

  • Damian Williams says:

    Kyle yes in the 2 years the tank has been setup I have never done a water change. When I first decided to go saltwater after the 10 years of freshwater experience I obviously did alot of reading and if I wanted to go marine then I was gonna have to find a way to make it affordable. My tank and sump hold approx 500litres of water. I should perform a 10% water change once a week which is 50litres. I also lose 25 litre in evaporation a week. 25litre of saltwater cost £7.50 and RO cost £4
    Putting me at £19 a week in just water. Far enough if I made it myself I would be a cheaper but still way more than I wanted to spend. I’m still oj the first bucket of salt I brought 2 years ago. I put approx half a cap of vodka in once a day and feed as much as I want. Skimmer pulls out some amazing plant food for the garden.

  • Damian Williams says:

    Mark it obviously been some months since I came across that theory so I’m having trouble figuring out where I read it. I only tried it cause I had run out of ideas and when I was told to increase temp to 80 my tank had always been at 80 so decided to just try it. I will have a good look and forward any articles I find your way. You’ve given me so much help it will be nice to repay the favour. Cheers

  • Richard Schmidt says:

    Vodka? I’m in! 2 cups for me and by then I will forget about giving any to the tank (until it pays for a bottle.) 🙂

  • ginger says:

    Mark, instead of having everyone battle over the ich problems and techniques to cure why don’t you tell us what you recommend. I’ve quarantined fish and when I put them in my tank….BAM…ich. Iv’e used ich treatment after ich treatment and it meses up my protein skimmer to the point of wanting to scream. I have a 150 gal reef and fish tank. Some ich treatments are safe for coral and inverts, some aren’t……I still want to scream! And don’t tell me to buy your book.

  • Joe says:


    Youre not supposed to use any filtration method when dosing medication.

    Skimmer temoves the meds thus redicibg its effectiveness. Carbon slso removes meds, reducing meds even further.

  • ginger says:

    Joe, I don’t have the skimmer on when I treat. It’s after the treatment and carbon…..

  • lori says:

    Just thought I’d put a reminder out there that I have used the above mentioned Dr. G’s caviar for well over a year now…I have a reef and fish tank…have added new fish etc. and have never had a problem with ich. Just a suggestion…don’t want to offend anyone. I know losing fish to ich can be so saddening.

  • Tom says:

    I too have been using the Dr. G’s Anti parasitic caviar to treat ich. I went to the Macna 2014 show in Denver and met Dr G at his booth. I was considering getting a Achilles Tang and was looking for a “new” type of medication to have on hand knowing it is inevitable that they come down with ich. He convinced me to try it. I purchased the medication before I bought the fish. Then after I bought the achilles tang I quarantined it for 8 weeks. Released it slowly using an acclimation box. Within 5 days he was showing ich. I started using the caviar daily, one capful, three times a day for eight weeks and IT WORKED. One thing I have noticed on several forums is that the fish wouldnt eat the caviar, I would suggest that if you have access to an Asian market, get some orange roe ( fish eggs) and feed it to the fish occasionally to mix things up. That way the fish never really know what they are getting. Also do not wait until your fish have a full blown ich infestation and try to use this as the fish usually have lost their appetite. This is a game changer and should be on hand by anyone who owns Tangs, Angels or any other Ich prone fish. Hope this helps

  • nicholas j elia says:

    I have dr g medication and they still have ick …… how does Dr g takes to work ?

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